Lab 8 Solutions.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Additional Regular Expression Functions and Stringi"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "scrolled": true
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "Registered S3 methods overwritten by 'ggplot2':\n",
      "  method         from \n",
      "  [.quosures     rlang\n",
      "  c.quosures     rlang\n",
      "  print.quosures rlang\n",
      "Registered S3 method overwritten by 'rvest':\n",
      "  method            from\n",
      "  read_xml.response xml2\n",
      "-- Attaching packages --------------------------------------- tidyverse 1.2.1 --\n",
      "v ggplot2 3.1.1       v purrr   0.3.2  \n",
      "v tibble  2.1.1       v dplyr   0.8.0.1\n",
      "v tidyr   0.8.3       v stringr 1.4.0  \n",
      "v readr   1.3.1       v forcats 0.4.0  \n",
      "-- Conflicts ------------------------------------------ tidyverse_conflicts() --\n",
      "x dplyr::filter() masks stats::filter()\n",
      "x dplyr::lag()    masks stats::lag()\n"
     ]
    }
   ],
   "source": [
    "library(tidyverse)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "test = c('text', 'text200withnum', '200')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "All str functions have the string as the first parameter, the pattern as the second, and then the rest are function dependent "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Str_detect: Returns true if the string contains the pattern, false otherwise"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<ol class=list-inline>\n",
       "\t<li>FALSE</li>\n",
       "\t<li>TRUE</li>\n",
       "\t<li>TRUE</li>\n",
       "</ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item FALSE\n",
       "\\item TRUE\n",
       "\\item TRUE\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. FALSE\n",
       "2. TRUE\n",
       "3. TRUE\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] FALSE  TRUE  TRUE"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "(str_detect(test, '\\\\d+')) # sum, which"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Str_replace: Replaces matched patterns in the string with a replacement"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [],
   "source": [
    "?str_replace"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<ol class=list-inline>\n",
       "\t<li>'text'</li>\n",
       "\t<li>'textXXwithnum'</li>\n",
       "\t<li>'XX'</li>\n",
       "</ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item 'text'\n",
       "\\item 'textXXwithnum'\n",
       "\\item 'XX'\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. 'text'\n",
       "2. 'textXXwithnum'\n",
       "3. 'XX'\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] \"text\"          \"textXXwithnum\" \"XX\"           "
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "str_replace(test, '\\\\d+', 'XX')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<ol class=list-inline>\n",
       "\t<li>'text'</li>\n",
       "\t<li>'textwithnum'</li>\n",
       "\t<li>''</li>\n",
       "</ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item 'text'\n",
       "\\item 'textwithnum'\n",
       "\\item ''\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. 'text'\n",
       "2. 'textwithnum'\n",
       "3. ''\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] \"text\"        \"textwithnum\" \"\"           "
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "str_replace(test, '\\\\d+', '') "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<ol class=list-inline>\n",
       "\t<li>'text'</li>\n",
       "\t<li>'textXXXwithnum'</li>\n",
       "\t<li>'XXX'</li>\n",
       "</ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item 'text'\n",
       "\\item 'textXXXwithnum'\n",
       "\\item 'XXX'\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. 'text'\n",
       "2. 'textXXXwithnum'\n",
       "3. 'XXX'\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] \"text\"           \"textXXXwithnum\" \"XXX\"           "
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "str_replace_all(test, '\\\\d', 'X') "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Str_extract: Get exactly the matching patterns"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<ol class=list-inline>\n",
       "\t<li>NA</li>\n",
       "\t<li>'200'</li>\n",
       "\t<li>'200'</li>\n",
       "</ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item NA\n",
       "\\item '200'\n",
       "\\item '200'\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. NA\n",
       "2. '200'\n",
       "3. '200'\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] NA    \"200\" \"200\""
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "str_extract(test, '\\\\d+')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Stringi\n",
    "\n",
    "- Stringr is built on top of the stringi package\n",
    "- Stringr covers most of our basic string neccessities\n",
    "- If you find yourself in a situation where you don't think any stringr function does what you want, a stringi function almost certainly will (49 vs. 250)\n",
    "- The functions work similarly for the most part: Just swap str_ for stri_"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Writing Functions"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We already have some experience calling functions that have been written for us. Sometimes you will want to do something that has no public implementation, so it makes sense to write your own function. A rule of thumb is that if you are planning to repeat the same operation several times, you should encapsulate that behaviour in a function. "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Basic Syntax"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "myfunction <- function(arg1, arg2, ... ){\n",
    "    statements\n",
    "    return(object)\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [],
   "source": [
    "say_hello <- function() {\n",
    "    \n",
    "    print(\"hello\")\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1] \"hello\"\n"
     ]
    }
   ],
   "source": [
    "say_hello()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [],
   "source": [
    "say_hello <- function(guest) {\n",
    "    \n",
    "    paste(\"ello\", guest)\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "'Hello Ariel'"
      ],
      "text/latex": [
       "'Hello Ariel'"
      ],
      "text/markdown": [
       "'Hello Ariel'"
      ],
      "text/plain": [
       "[1] \"Hello Ariel\""
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "say_hello(\"Ariel\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [],
   "source": [
    "say_something <- function(word1 = \"hello\", word2 = \"world\") {\n",
    "    \n",
    "    paste(word1, word2)\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "'hello world'"
      ],
      "text/latex": [
       "'hello world'"
      ],
      "text/markdown": [
       "'hello world'"
      ],
      "text/plain": [
       "[1] \"hello world\""
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "say_something()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "metadata": {},
   "outputs": [],
   "source": [
    "add_numbers <- function(x, y) {\n",
    "    \n",
    "    x + y # return\n",
    "    x - y\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "-1"
      ],
      "text/latex": [
       "-1"
      ],
      "text/markdown": [
       "-1"
      ],
      "text/plain": [
       "[1] -1"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "add_numbers(3, 4)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example: Rescaling Data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 53,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "# A tibble: 10 x 4\n",
      "        a       b       c      d\n",
      "    <dbl>   <dbl>   <dbl>  <dbl>\n",
      " 1  0.702  0.0956  1.46    0.356\n",
      " 2 -0.228  1.81   -0.195  -0.567\n",
      " 3 -2.84  -0.553  -0.252   0.477\n",
      " 4 -0.568  1.02    0.450   0.345\n",
      " 5  0.377  0.660   0.488   2.44 \n",
      " 6  1.14  -0.392  -1.04    0.250\n",
      " 7 -0.545  1.42   -0.0298  0.287\n",
      " 8 -0.166 -0.234   0.815  -0.401\n",
      " 9 -0.472 -0.957   1.50    0.546\n",
      "10 -0.660  0.593  -1.08   -0.854\n"
     ]
    }
   ],
   "source": [
    "df = tibble(\n",
    "  a = rnorm(10),\n",
    "  b = rnorm(10),\n",
    "  c = rnorm(10),\n",
    "  d = rnorm(10)\n",
    ")\n",
    "\n",
    "print(df)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "For every data point, we want to subtract the smallest number in the column and then divide by the range."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 60,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "# A tibble: 10 x 4\n",
      "       a     b      c      d\n",
      "   <dbl> <dbl>  <dbl>  <dbl>\n",
      " 1 0.891 0.380 0.982  0.367 \n",
      " 2 0.657 1     0.342  0.0870\n",
      " 3 0     0.146 0.320  0.404 \n",
      " 4 0.571 0.712 0.592  0.364 \n",
      " 5 0.809 0.584 0.607  1     \n",
      " 6 1     0.204 0.0154 0.335 \n",
      " 7 0.577 0.859 0.406  0.346 \n",
      " 8 0.672 0.261 0.734  0.137 \n",
      " 9 0.596 0     1      0.425 \n",
      "10 0.548 0.560 0      0     \n"
     ]
    }
   ],
   "source": [
    "df2 = df %>% \n",
    "    mutate(a = (a-min(a))/(max(a)-min(a)),\n",
    "           b = (b-min(b))/(max(b)-min(b)),\n",
    "           c = (c-min(c))/(max(c)-min(c)),\n",
    "           d = (d-min(d))/(max(d)-min(d)))\n",
    " \n",
    "print(df2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 64,
   "metadata": {},
   "outputs": [],
   "source": [
    "rescale = function(x) {\n",
    "    (x - min(x)) / (max(x) - min(x))\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {},
   "outputs": [],
   "source": [
    "df2 = df %>%\n",
    "    mutate(a=rescale(a), b=rescale(b), c=rescale(c), d=rescale(d))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 63,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "# A tibble: 10 x 4\n",
      "       a     b      c      d\n",
      "   <dbl> <dbl>  <dbl>  <dbl>\n",
      " 1 0.891 0.380 0.982  0.367 \n",
      " 2 0.657 1     0.342  0.0870\n",
      " 3 0     0.146 0.320  0.404 \n",
      " 4 0.571 0.712 0.592  0.364 \n",
      " 5 0.809 0.584 0.607  1     \n",
      " 6 1     0.204 0.0154 0.335 \n",
      " 7 0.577 0.859 0.406  0.346 \n",
      " 8 0.672 0.261 0.734  0.137 \n",
      " 9 0.596 0     1      0.425 \n",
      "10 0.548 0.560 0      0     \n"
     ]
    }
   ],
   "source": [
    "print(df2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Conditional Execution"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Often when writing functions we need to do different things depending on what data is passed in. This is known as *conditional execution*, and is accomplished using the `if/else` construct:\n",
    "```{r}\n",
    "if (condition) {\n",
    "  # code executed when condition is TRUE\n",
    "} else {\n",
    "  # code executed when condition is FALSE\n",
    "}\n",
    "```\n",
    "\n",
    "We already saw an example of this type of behavior with the if_else fuction. "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Example\n",
    "The *Heaviside step function* is defined as\n",
    "$$H(x)=\\begin{cases}0,&x\\le 0\\\\\n",
    "1,&\\text{otherwise}\n",
    "\\end{cases}.$$\n",
    "How can we code this as an R function?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 67,
   "metadata": {},
   "outputs": [],
   "source": [
    "H = function(x) {\n",
    "    \n",
    "    if (x <= 0) {\n",
    "        return(0)\n",
    "    } else {\n",
    "        return(1)\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 68,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "0"
      ],
      "text/latex": [
       "0"
      ],
      "text/markdown": [
       "0"
      ],
      "text/plain": [
       "[1] 0"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "H(0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 69,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "1"
      ],
      "text/latex": [
       "1"
      ],
      "text/markdown": [
       "1"
      ],
      "text/plain": [
       "[1] 1"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "H(1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 70,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "1"
      ],
      "text/latex": [
       "1"
      ],
      "text/markdown": [
       "1"
      ],
      "text/plain": [
       "[1] 1"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "H(2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 71,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "0"
      ],
      "text/latex": [
       "0"
      ],
      "text/markdown": [
       "0"
      ],
      "text/plain": [
       "[1] 0"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "H(-1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Multiple conditions\n",
    "Sometimes you will want to check multiple conditions using an `if` statement. For example, let's define the function $$\\operatorname{sgn}(x) = \\begin{cases}-1,&x<0\\\\0,&x=0\\\\1,&x>0.\\end{cases}$$"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 72,
   "metadata": {},
   "outputs": [],
   "source": [
    "sgn = function(x) {\n",
    "    if (x < 0) {\n",
    "        return(-1)\n",
    "    } else if (x == 0) {\n",
    "        return(0)\n",
    "    } else {\n",
    "        return(1)\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 73,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "1"
      ],
      "text/latex": [
       "1"
      ],
      "text/markdown": [
       "1"
      ],
      "text/plain": [
       "[1] 1"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "sgn(2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 74,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "0"
      ],
      "text/latex": [
       "0"
      ],
      "text/markdown": [
       "0"
      ],
      "text/plain": [
       "[1] 0"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "sgn(0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 75,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "-1"
      ],
      "text/latex": [
       "-1"
      ],
      "text/markdown": [
       "-1"
      ],
      "text/plain": [
       "[1] -1"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "sgn(-2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The general form is\n",
    "```{r}\n",
    "if (condition1) {\n",
    "  # do something\n",
    "} else if (condition2) {\n",
    "  # do something else\n",
    "} else {\n",
    "  # do another thing\n",
    "}\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Validation\n",
    "When writing functions it's a good idea to *validate* the input -- that is, make sure it matches your assumptions about what is being passed to the function. Consider the following function which returns the weighted average of a vector:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 79,
   "metadata": {},
   "outputs": [],
   "source": [
    "w_mean = function(x, w) {\n",
    "    sum(x * w) / sum(w)\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 81,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "2.3"
      ],
      "text/latex": [
       "2.3"
      ],
      "text/markdown": [
       "2.3"
      ],
      "text/plain": [
       "[1] 2.3"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "w_mean(x = c(1,2,3,4), w = c(.2, .4, .3, .1))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 82,
   "metadata": {},
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "Warning message in x * w:\n",
      "\"longer object length is not a multiple of shorter object length\""
     ]
    },
    {
     "data": {
      "text/html": [
       "2.66666666666667"
      ],
      "text/latex": [
       "2.66666666666667"
      ],
      "text/markdown": [
       "2.66666666666667"
      ],
      "text/plain": [
       "[1] 2.666667"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "w_mean(c(1,2,3), w=c(1, 2))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 83,
   "metadata": {},
   "outputs": [],
   "source": [
    "w_mean = function(x, w) {\n",
    "    stopifnot(length(w) == length(x))\n",
    "    sum(x * w) / sum(w)\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 84,
   "metadata": {},
   "outputs": [
    {
     "ename": "ERROR",
     "evalue": "Error in w_mean(c(1, 2, 3), w = c(1, 2)): length(w) == length(x) is not TRUE\n",
     "output_type": "error",
     "traceback": [
      "Error in w_mean(c(1, 2, 3), w = c(1, 2)): length(w) == length(x) is not TRUE\nTraceback:\n",
      "1. w_mean(c(1, 2, 3), w = c(1, 2))",
      "2. stopifnot(length(w) == length(x))   # at line 2 of file <text>"
     ]
    }
   ],
   "source": [
    "w_mean(c(1,2,3), w=c(1, 2))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 85,
   "metadata": {},
   "outputs": [
    {
     "ename": "ERROR",
     "evalue": "Error in w_mean(c(1, 2, 3), c(1, 2)): length of data and weight vector do not match\n",
     "output_type": "error",
     "traceback": [
      "Error in w_mean(c(1, 2, 3), c(1, 2)): length of data and weight vector do not match\nTraceback:\n",
      "1. w_mean(c(1, 2, 3), c(1, 2))",
      "2. stop(\"length of data and weight vector do not match\")   # at line 3 of file <text>"
     ]
    }
   ],
   "source": [
    "w_mean = function(x, w) {\n",
    "    if (length(w) != length(x)) {\n",
    "        stop('length of data and weight vector do not match')\n",
    "    }\n",
    "    (x * w) / sum(w)\n",
    "}\n",
    "\n",
    "w_mean(c(1,2,3), c(1, 2))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "###  Dot-dot-dot (`…`)\n",
    "Some functions are designed to take a variable number of inputs. We saw this for example with the `str_c` function."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To construct a function that takes a variable number of arguments we use the `...` notation:\n",
    "```{r}\n",
    "f = function(...) {\n",
    "    <do something with variable arguments>\n",
    "}\n",
    "```"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 88,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "'a, b, c, d, e, f, g, h, i, j'"
      ],
      "text/latex": [
       "'a, b, c, d, e, f, g, h, i, j'"
      ],
      "text/markdown": [
       "'a, b, c, d, e, f, g, h, i, j'"
      ],
      "text/plain": [
       "[1] \"a, b, c, d, e, f, g, h, i, j\""
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "commas <- function(...) {\n",
    "    str_c(..., collapse = \", \")\n",
    "}\n",
    "commas(letters[1:10])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Can you get away with just using a fixed amount of vectors?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Pipeable functions\n",
    "We've seen a lot of uses of the pipe operator `%>%`. As you become more advanced, you may find it useful to create your own functions which can be used in data pipelines. "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Transformations\n",
    "For pipeable functions that transform a data frame, simply return the altered version of the data frame. For example:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 91,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "# A tibble: 3 x 2\n",
      "      x y    \n",
      "  <dbl> <chr>\n",
      "1     1 a    \n",
      "2     2 b    \n",
      "3     3 c    \n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "<thead><tr><th scope=col>x</th><th scope=col>y</th></tr></thead>\n",
       "<tbody>\n",
       "\t<tr><td>1</td><td>a</td></tr>\n",
       "</tbody>\n",
       "</table>\n"
      ],
      "text/latex": [
       "\\begin{tabular}{r|ll}\n",
       " x & y\\\\\n",
       "\\hline\n",
       "\t 1 & a\\\\\n",
       "\\end{tabular}\n"
      ],
      "text/markdown": [
       "\n",
       "| x | y |\n",
       "|---|---|\n",
       "| 1 | a |\n",
       "\n"
      ],
      "text/plain": [
       "  x y\n",
       "1 1 a"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "<thead><tr><th scope=col>x</th><th scope=col>y</th></tr></thead>\n",
       "<tbody>\n",
       "\t<tr><td>3</td><td>c</td></tr>\n",
       "</tbody>\n",
       "</table>\n"
      ],
      "text/latex": [
       "\\begin{tabular}{r|ll}\n",
       " x & y\\\\\n",
       "\\hline\n",
       "\t 3 & c\\\\\n",
       "\\end{tabular}\n"
      ],
      "text/markdown": [
       "\n",
       "| x | y |\n",
       "|---|---|\n",
       "| 3 | c |\n",
       "\n"
      ],
      "text/plain": [
       "  x y\n",
       "1 3 c"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "get_row <- function(df, n=1) {\n",
    "    df %>% slice(n)\n",
    "}\n",
    "\n",
    "mydf = tibble(x=c(1,2,3), y=c(\"a\",\"b\",\"c\"))\n",
    "print(mydf)\n",
    "\n",
    "mydf %>% get_row()\n",
    "mydf %>% get_row(3)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Side effects\n",
    "Some functions have *side effects* but don't modify the original data frame. For example, consider the following function which counts how many missing values are present in a data frame:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 92,
   "metadata": {},
   "outputs": [],
   "source": [
    "show_missings = function(df) {\n",
    "  n <- sum(is.na(df))\n",
    "  cat(\"Missing values: \", n, \"\\n\", sep = \"\")\n",
    "  df  # note return value\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 93,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Missing values: 0\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<table>\n",
       "<thead><tr><th scope=col>manufacturer</th><th scope=col>model</th><th scope=col>displ</th><th scope=col>year</th><th scope=col>cyl</th><th scope=col>trans</th><th scope=col>drv</th><th scope=col>cty</th><th scope=col>hwy</th><th scope=col>fl</th><th scope=col>class</th></tr></thead>\n",
       "<tbody>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>1.8               </td><td>1999              </td><td>4                 </td><td>auto(l5)          </td><td>f                 </td><td>18                </td><td>29                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>1.8               </td><td>1999              </td><td>4                 </td><td>manual(m5)        </td><td>f                 </td><td>21                </td><td>29                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>2.0               </td><td>2008              </td><td>4                 </td><td>manual(m6)        </td><td>f                 </td><td>20                </td><td>31                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>2.0               </td><td>2008              </td><td>4                 </td><td>auto(av)          </td><td>f                 </td><td>21                </td><td>30                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>2.8               </td><td>1999              </td><td>6                 </td><td>auto(l5)          </td><td>f                 </td><td>16                </td><td>26                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>2.8               </td><td>1999              </td><td>6                 </td><td>manual(m5)        </td><td>f                 </td><td>18                </td><td>26                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4                </td><td>3.1               </td><td>2008              </td><td>6                 </td><td>auto(av)          </td><td>f                 </td><td>18                </td><td>27                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>1.8               </td><td>1999              </td><td>4                 </td><td>manual(m5)        </td><td>4                 </td><td>18                </td><td>26                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>1.8               </td><td>1999              </td><td>4                 </td><td>auto(l5)          </td><td>4                 </td><td>16                </td><td>25                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>2.0               </td><td>2008              </td><td>4                 </td><td>manual(m6)        </td><td>4                 </td><td>20                </td><td>28                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>2.0               </td><td>2008              </td><td>4                 </td><td>auto(s6)          </td><td>4                 </td><td>19                </td><td>27                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>2.8               </td><td>1999              </td><td>6                 </td><td>auto(l5)          </td><td>4                 </td><td>15                </td><td>25                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>2.8               </td><td>1999              </td><td>6                 </td><td>manual(m5)        </td><td>4                 </td><td>17                </td><td>25                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>3.1               </td><td>2008              </td><td>6                 </td><td>auto(s6)          </td><td>4                 </td><td>17                </td><td>25                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a4 quattro        </td><td>3.1               </td><td>2008              </td><td>6                 </td><td>manual(m6)        </td><td>4                 </td><td>15                </td><td>25                </td><td>p                 </td><td>compact           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a6 quattro        </td><td>2.8               </td><td>1999              </td><td>6                 </td><td>auto(l5)          </td><td>4                 </td><td>15                </td><td>24                </td><td>p                 </td><td>midsize           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a6 quattro        </td><td>3.1               </td><td>2008              </td><td>6                 </td><td>auto(s6)          </td><td>4                 </td><td>17                </td><td>25                </td><td>p                 </td><td>midsize           </td></tr>\n",
       "\t<tr><td>audi              </td><td>a6 quattro        </td><td>4.2               </td><td>2008              </td><td>8                 </td><td>auto(s6)          </td><td>4                 </td><td>16                </td><td>23                </td><td>p                 </td><td>midsize           </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>c1500 suburban 2wd</td><td>5.3               </td><td>2008              </td><td>8                 </td><td>auto(l4)          </td><td>r                 </td><td>14                </td><td>20                </td><td>r                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>c1500 suburban 2wd</td><td>5.3               </td><td>2008              </td><td>8                 </td><td>auto(l4)          </td><td>r                 </td><td>11                </td><td>15                </td><td>e                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>c1500 suburban 2wd</td><td>5.3               </td><td>2008              </td><td>8                 </td><td>auto(l4)          </td><td>r                 </td><td>14                </td><td>20                </td><td>r                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>c1500 suburban 2wd</td><td>5.7               </td><td>1999              </td><td>8                 </td><td>auto(l4)          </td><td>r                 </td><td>13                </td><td>17                </td><td>r                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>c1500 suburban 2wd</td><td>6.0               </td><td>2008              </td><td>8                 </td><td>auto(l4)          </td><td>r                 </td><td>12                </td><td>17                </td><td>r                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>corvette          </td><td>5.7               </td><td>1999              </td><td>8                 </td><td>manual(m6)        </td><td>r                 </td><td>16                </td><td>26                </td><td>p                 </td><td>2seater           </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>corvette          </td><td>5.7               </td><td>1999              </td><td>8                 </td><td>auto(l4)          </td><td>r                 </td><td>15                </td><td>23                </td><td>p                 </td><td>2seater           </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>corvette          </td><td>6.2               </td><td>2008              </td><td>8                 </td><td>manual(m6)        </td><td>r                 </td><td>16                </td><td>26                </td><td>p                 </td><td>2seater           </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>corvette          </td><td>6.2               </td><td>2008              </td><td>8                 </td><td>auto(s6)          </td><td>r                 </td><td>15                </td><td>25                </td><td>p                 </td><td>2seater           </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>corvette          </td><td>7.0               </td><td>2008              </td><td>8                 </td><td>manual(m6)        </td><td>r                 </td><td>15                </td><td>24                </td><td>p                 </td><td>2seater           </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>k1500 tahoe 4wd   </td><td>5.3               </td><td>2008              </td><td>8                 </td><td>auto(l4)          </td><td>4                 </td><td>14                </td><td>19                </td><td>r                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>chevrolet         </td><td>k1500 tahoe 4wd   </td><td>5.3               </td><td>2008              </td><td>8                 </td><td>auto(l4)          </td><td>4                 </td><td>11                </td><td>14                </td><td>e                 </td><td>suv               </td></tr>\n",
       "\t<tr><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr>\n",
       "\t<tr><td>toyota           </td><td>toyota tacoma 4wd</td><td>3.4              </td><td>1999             </td><td>6                </td><td>auto(l4)         </td><td>4                </td><td>15               </td><td>19               </td><td>r                </td><td>pickup           </td></tr>\n",
       "\t<tr><td>toyota           </td><td>toyota tacoma 4wd</td><td>4.0              </td><td>2008             </td><td>6                </td><td>manual(m6)       </td><td>4                </td><td>15               </td><td>18               </td><td>r                </td><td>pickup           </td></tr>\n",
       "\t<tr><td>toyota           </td><td>toyota tacoma 4wd</td><td>4.0              </td><td>2008             </td><td>6                </td><td>auto(l5)         </td><td>4                </td><td>16               </td><td>20               </td><td>r                </td><td>pickup           </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>gti              </td><td>2.0              </td><td>1999             </td><td>4                </td><td>manual(m5)       </td><td>f                </td><td>21               </td><td>29               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>gti              </td><td>2.0              </td><td>1999             </td><td>4                </td><td>auto(l4)         </td><td>f                </td><td>19               </td><td>26               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>gti              </td><td>2.0              </td><td>2008             </td><td>4                </td><td>manual(m6)       </td><td>f                </td><td>21               </td><td>29               </td><td>p                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>gti              </td><td>2.0              </td><td>2008             </td><td>4                </td><td>auto(s6)         </td><td>f                </td><td>22               </td><td>29               </td><td>p                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>gti              </td><td>2.8              </td><td>1999             </td><td>6                </td><td>manual(m5)       </td><td>f                </td><td>17               </td><td>24               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>1.9              </td><td>1999             </td><td>4                </td><td>manual(m5)       </td><td>f                </td><td>33               </td><td>44               </td><td>d                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.0              </td><td>1999             </td><td>4                </td><td>manual(m5)       </td><td>f                </td><td>21               </td><td>29               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.0              </td><td>1999             </td><td>4                </td><td>auto(l4)         </td><td>f                </td><td>19               </td><td>26               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.0              </td><td>2008             </td><td>4                </td><td>auto(s6)         </td><td>f                </td><td>22               </td><td>29               </td><td>p                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.0              </td><td>2008             </td><td>4                </td><td>manual(m6)       </td><td>f                </td><td>21               </td><td>29               </td><td>p                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.5              </td><td>2008             </td><td>5                </td><td>auto(s6)         </td><td>f                </td><td>21               </td><td>29               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.5              </td><td>2008             </td><td>5                </td><td>manual(m5)       </td><td>f                </td><td>21               </td><td>29               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.8              </td><td>1999             </td><td>6                </td><td>auto(l4)         </td><td>f                </td><td>16               </td><td>23               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>jetta            </td><td>2.8              </td><td>1999             </td><td>6                </td><td>manual(m5)       </td><td>f                </td><td>17               </td><td>24               </td><td>r                </td><td>compact          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>new beetle       </td><td>1.9              </td><td>1999             </td><td>4                </td><td>manual(m5)       </td><td>f                </td><td>35               </td><td>44               </td><td>d                </td><td>subcompact       </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>new beetle       </td><td>1.9              </td><td>1999             </td><td>4                </td><td>auto(l4)         </td><td>f                </td><td>29               </td><td>41               </td><td>d                </td><td>subcompact       </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>new beetle       </td><td>2.0              </td><td>1999             </td><td>4                </td><td>manual(m5)       </td><td>f                </td><td>21               </td><td>29               </td><td>r                </td><td>subcompact       </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>new beetle       </td><td>2.0              </td><td>1999             </td><td>4                </td><td>auto(l4)         </td><td>f                </td><td>19               </td><td>26               </td><td>r                </td><td>subcompact       </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>new beetle       </td><td>2.5              </td><td>2008             </td><td>5                </td><td>manual(m5)       </td><td>f                </td><td>20               </td><td>28               </td><td>r                </td><td>subcompact       </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>new beetle       </td><td>2.5              </td><td>2008             </td><td>5                </td><td>auto(s6)         </td><td>f                </td><td>20               </td><td>29               </td><td>r                </td><td>subcompact       </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>1.8              </td><td>1999             </td><td>4                </td><td>manual(m5)       </td><td>f                </td><td>21               </td><td>29               </td><td>p                </td><td>midsize          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>1.8              </td><td>1999             </td><td>4                </td><td>auto(l5)         </td><td>f                </td><td>18               </td><td>29               </td><td>p                </td><td>midsize          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>2.0              </td><td>2008             </td><td>4                </td><td>auto(s6)         </td><td>f                </td><td>19               </td><td>28               </td><td>p                </td><td>midsize          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>2.0              </td><td>2008             </td><td>4                </td><td>manual(m6)       </td><td>f                </td><td>21               </td><td>29               </td><td>p                </td><td>midsize          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>2.8              </td><td>1999             </td><td>6                </td><td>auto(l5)         </td><td>f                </td><td>16               </td><td>26               </td><td>p                </td><td>midsize          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>2.8              </td><td>1999             </td><td>6                </td><td>manual(m5)       </td><td>f                </td><td>18               </td><td>26               </td><td>p                </td><td>midsize          </td></tr>\n",
       "\t<tr><td>volkswagen       </td><td>passat           </td><td>3.6              </td><td>2008             </td><td>6                </td><td>auto(s6)         </td><td>f                </td><td>17               </td><td>26               </td><td>p                </td><td>midsize          </td></tr>\n",
       "</tbody>\n",
       "</table>\n"
      ],
      "text/latex": [
       "\\begin{tabular}{r|lllllllllll}\n",
       " manufacturer & model & displ & year & cyl & trans & drv & cty & hwy & fl & class\\\\\n",
       "\\hline\n",
       "\t audi               & a4                 & 1.8                & 1999               & 4                  & auto(l5)           & f                  & 18                 & 29                 & p                  & compact           \\\\\n",
       "\t audi               & a4                 & 1.8                & 1999               & 4                  & manual(m5)         & f                  & 21                 & 29                 & p                  & compact           \\\\\n",
       "\t audi               & a4                 & 2.0                & 2008               & 4                  & manual(m6)         & f                  & 20                 & 31                 & p                  & compact           \\\\\n",
       "\t audi               & a4                 & 2.0                & 2008               & 4                  & auto(av)           & f                  & 21                 & 30                 & p                  & compact           \\\\\n",
       "\t audi               & a4                 & 2.8                & 1999               & 6                  & auto(l5)           & f                  & 16                 & 26                 & p                  & compact           \\\\\n",
       "\t audi               & a4                 & 2.8                & 1999               & 6                  & manual(m5)         & f                  & 18                 & 26                 & p                  & compact           \\\\\n",
       "\t audi               & a4                 & 3.1                & 2008               & 6                  & auto(av)           & f                  & 18                 & 27                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 1.8                & 1999               & 4                  & manual(m5)         & 4                  & 18                 & 26                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 1.8                & 1999               & 4                  & auto(l5)           & 4                  & 16                 & 25                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 2.0                & 2008               & 4                  & manual(m6)         & 4                  & 20                 & 28                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 2.0                & 2008               & 4                  & auto(s6)           & 4                  & 19                 & 27                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 2.8                & 1999               & 6                  & auto(l5)           & 4                  & 15                 & 25                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 2.8                & 1999               & 6                  & manual(m5)         & 4                  & 17                 & 25                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 3.1                & 2008               & 6                  & auto(s6)           & 4                  & 17                 & 25                 & p                  & compact           \\\\\n",
       "\t audi               & a4 quattro         & 3.1                & 2008               & 6                  & manual(m6)         & 4                  & 15                 & 25                 & p                  & compact           \\\\\n",
       "\t audi               & a6 quattro         & 2.8                & 1999               & 6                  & auto(l5)           & 4                  & 15                 & 24                 & p                  & midsize           \\\\\n",
       "\t audi               & a6 quattro         & 3.1                & 2008               & 6                  & auto(s6)           & 4                  & 17                 & 25                 & p                  & midsize           \\\\\n",
       "\t audi               & a6 quattro         & 4.2                & 2008               & 8                  & auto(s6)           & 4                  & 16                 & 23                 & p                  & midsize           \\\\\n",
       "\t chevrolet          & c1500 suburban 2wd & 5.3                & 2008               & 8                  & auto(l4)           & r                  & 14                 & 20                 & r                  & suv               \\\\\n",
       "\t chevrolet          & c1500 suburban 2wd & 5.3                & 2008               & 8                  & auto(l4)           & r                  & 11                 & 15                 & e                  & suv               \\\\\n",
       "\t chevrolet          & c1500 suburban 2wd & 5.3                & 2008               & 8                  & auto(l4)           & r                  & 14                 & 20                 & r                  & suv               \\\\\n",
       "\t chevrolet          & c1500 suburban 2wd & 5.7                & 1999               & 8                  & auto(l4)           & r                  & 13                 & 17                 & r                  & suv               \\\\\n",
       "\t chevrolet          & c1500 suburban 2wd & 6.0                & 2008               & 8                  & auto(l4)           & r                  & 12                 & 17                 & r                  & suv               \\\\\n",
       "\t chevrolet          & corvette           & 5.7                & 1999               & 8                  & manual(m6)         & r                  & 16                 & 26                 & p                  & 2seater           \\\\\n",
       "\t chevrolet          & corvette           & 5.7                & 1999               & 8                  & auto(l4)           & r                  & 15                 & 23                 & p                  & 2seater           \\\\\n",
       "\t chevrolet          & corvette           & 6.2                & 2008               & 8                  & manual(m6)         & r                  & 16                 & 26                 & p                  & 2seater           \\\\\n",
       "\t chevrolet          & corvette           & 6.2                & 2008               & 8                  & auto(s6)           & r                  & 15                 & 25                 & p                  & 2seater           \\\\\n",
       "\t chevrolet          & corvette           & 7.0                & 2008               & 8                  & manual(m6)         & r                  & 15                 & 24                 & p                  & 2seater           \\\\\n",
       "\t chevrolet          & k1500 tahoe 4wd    & 5.3                & 2008               & 8                  & auto(l4)           & 4                  & 14                 & 19                 & r                  & suv               \\\\\n",
       "\t chevrolet          & k1500 tahoe 4wd    & 5.3                & 2008               & 8                  & auto(l4)           & 4                  & 11                 & 14                 & e                  & suv               \\\\\n",
       "\t ... & ... & ... & ... & ... & ... & ... & ... & ... & ... & ...\\\\\n",
       "\t toyota            & toyota tacoma 4wd & 3.4               & 1999              & 6                 & auto(l4)          & 4                 & 15                & 19                & r                 & pickup           \\\\\n",
       "\t toyota            & toyota tacoma 4wd & 4.0               & 2008              & 6                 & manual(m6)        & 4                 & 15                & 18                & r                 & pickup           \\\\\n",
       "\t toyota            & toyota tacoma 4wd & 4.0               & 2008              & 6                 & auto(l5)          & 4                 & 16                & 20                & r                 & pickup           \\\\\n",
       "\t volkswagen        & gti               & 2.0               & 1999              & 4                 & manual(m5)        & f                 & 21                & 29                & r                 & compact          \\\\\n",
       "\t volkswagen        & gti               & 2.0               & 1999              & 4                 & auto(l4)          & f                 & 19                & 26                & r                 & compact          \\\\\n",
       "\t volkswagen        & gti               & 2.0               & 2008              & 4                 & manual(m6)        & f                 & 21                & 29                & p                 & compact          \\\\\n",
       "\t volkswagen        & gti               & 2.0               & 2008              & 4                 & auto(s6)          & f                 & 22                & 29                & p                 & compact          \\\\\n",
       "\t volkswagen        & gti               & 2.8               & 1999              & 6                 & manual(m5)        & f                 & 17                & 24                & r                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 1.9               & 1999              & 4                 & manual(m5)        & f                 & 33                & 44                & d                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.0               & 1999              & 4                 & manual(m5)        & f                 & 21                & 29                & r                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.0               & 1999              & 4                 & auto(l4)          & f                 & 19                & 26                & r                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.0               & 2008              & 4                 & auto(s6)          & f                 & 22                & 29                & p                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.0               & 2008              & 4                 & manual(m6)        & f                 & 21                & 29                & p                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.5               & 2008              & 5                 & auto(s6)          & f                 & 21                & 29                & r                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.5               & 2008              & 5                 & manual(m5)        & f                 & 21                & 29                & r                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.8               & 1999              & 6                 & auto(l4)          & f                 & 16                & 23                & r                 & compact          \\\\\n",
       "\t volkswagen        & jetta             & 2.8               & 1999              & 6                 & manual(m5)        & f                 & 17                & 24                & r                 & compact          \\\\\n",
       "\t volkswagen        & new beetle        & 1.9               & 1999              & 4                 & manual(m5)        & f                 & 35                & 44                & d                 & subcompact       \\\\\n",
       "\t volkswagen        & new beetle        & 1.9               & 1999              & 4                 & auto(l4)          & f                 & 29                & 41                & d                 & subcompact       \\\\\n",
       "\t volkswagen        & new beetle        & 2.0               & 1999              & 4                 & manual(m5)        & f                 & 21                & 29                & r                 & subcompact       \\\\\n",
       "\t volkswagen        & new beetle        & 2.0               & 1999              & 4                 & auto(l4)          & f                 & 19                & 26                & r                 & subcompact       \\\\\n",
       "\t volkswagen        & new beetle        & 2.5               & 2008              & 5                 & manual(m5)        & f                 & 20                & 28                & r                 & subcompact       \\\\\n",
       "\t volkswagen        & new beetle        & 2.5               & 2008              & 5                 & auto(s6)          & f                 & 20                & 29                & r                 & subcompact       \\\\\n",
       "\t volkswagen        & passat            & 1.8               & 1999              & 4                 & manual(m5)        & f                 & 21                & 29                & p                 & midsize          \\\\\n",
       "\t volkswagen        & passat            & 1.8               & 1999              & 4                 & auto(l5)          & f                 & 18                & 29                & p                 & midsize          \\\\\n",
       "\t volkswagen        & passat            & 2.0               & 2008              & 4                 & auto(s6)          & f                 & 19                & 28                & p                 & midsize          \\\\\n",
       "\t volkswagen        & passat            & 2.0               & 2008              & 4                 & manual(m6)        & f                 & 21                & 29                & p                 & midsize          \\\\\n",
       "\t volkswagen        & passat            & 2.8               & 1999              & 6                 & auto(l5)          & f                 & 16                & 26                & p                 & midsize          \\\\\n",
       "\t volkswagen        & passat            & 2.8               & 1999              & 6                 & manual(m5)        & f                 & 18                & 26                & p                 & midsize          \\\\\n",
       "\t volkswagen        & passat            & 3.6               & 2008              & 6                 & auto(s6)          & f                 & 17                & 26                & p                 & midsize          \\\\\n",
       "\\end{tabular}\n"
      ],
      "text/markdown": [
       "\n",
       "| manufacturer | model | displ | year | cyl | trans | drv | cty | hwy | fl | class |\n",
       "|---|---|---|---|---|---|---|---|---|---|---|\n",
       "| audi               | a4                 | 1.8                | 1999               | 4                  | auto(l5)           | f                  | 18                 | 29                 | p                  | compact            |\n",
       "| audi               | a4                 | 1.8                | 1999               | 4                  | manual(m5)         | f                  | 21                 | 29                 | p                  | compact            |\n",
       "| audi               | a4                 | 2.0                | 2008               | 4                  | manual(m6)         | f                  | 20                 | 31                 | p                  | compact            |\n",
       "| audi               | a4                 | 2.0                | 2008               | 4                  | auto(av)           | f                  | 21                 | 30                 | p                  | compact            |\n",
       "| audi               | a4                 | 2.8                | 1999               | 6                  | auto(l5)           | f                  | 16                 | 26                 | p                  | compact            |\n",
       "| audi               | a4                 | 2.8                | 1999               | 6                  | manual(m5)         | f                  | 18                 | 26                 | p                  | compact            |\n",
       "| audi               | a4                 | 3.1                | 2008               | 6                  | auto(av)           | f                  | 18                 | 27                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 1.8                | 1999               | 4                  | manual(m5)         | 4                  | 18                 | 26                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 1.8                | 1999               | 4                  | auto(l5)           | 4                  | 16                 | 25                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 2.0                | 2008               | 4                  | manual(m6)         | 4                  | 20                 | 28                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 2.0                | 2008               | 4                  | auto(s6)           | 4                  | 19                 | 27                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 2.8                | 1999               | 6                  | auto(l5)           | 4                  | 15                 | 25                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 2.8                | 1999               | 6                  | manual(m5)         | 4                  | 17                 | 25                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 3.1                | 2008               | 6                  | auto(s6)           | 4                  | 17                 | 25                 | p                  | compact            |\n",
       "| audi               | a4 quattro         | 3.1                | 2008               | 6                  | manual(m6)         | 4                  | 15                 | 25                 | p                  | compact            |\n",
       "| audi               | a6 quattro         | 2.8                | 1999               | 6                  | auto(l5)           | 4                  | 15                 | 24                 | p                  | midsize            |\n",
       "| audi               | a6 quattro         | 3.1                | 2008               | 6                  | auto(s6)           | 4                  | 17                 | 25                 | p                  | midsize            |\n",
       "| audi               | a6 quattro         | 4.2                | 2008               | 8                  | auto(s6)           | 4                  | 16                 | 23                 | p                  | midsize            |\n",
       "| chevrolet          | c1500 suburban 2wd | 5.3                | 2008               | 8                  | auto(l4)           | r                  | 14                 | 20                 | r                  | suv                |\n",
       "| chevrolet          | c1500 suburban 2wd | 5.3                | 2008               | 8                  | auto(l4)           | r                  | 11                 | 15                 | e                  | suv                |\n",
       "| chevrolet          | c1500 suburban 2wd | 5.3                | 2008               | 8                  | auto(l4)           | r                  | 14                 | 20                 | r                  | suv                |\n",
       "| chevrolet          | c1500 suburban 2wd | 5.7                | 1999               | 8                  | auto(l4)           | r                  | 13                 | 17                 | r                  | suv                |\n",
       "| chevrolet          | c1500 suburban 2wd | 6.0                | 2008               | 8                  | auto(l4)           | r                  | 12                 | 17                 | r                  | suv                |\n",
       "| chevrolet          | corvette           | 5.7                | 1999               | 8                  | manual(m6)         | r                  | 16                 | 26                 | p                  | 2seater            |\n",
       "| chevrolet          | corvette           | 5.7                | 1999               | 8                  | auto(l4)           | r                  | 15                 | 23                 | p                  | 2seater            |\n",
       "| chevrolet          | corvette           | 6.2                | 2008               | 8                  | manual(m6)         | r                  | 16                 | 26                 | p                  | 2seater            |\n",
       "| chevrolet          | corvette           | 6.2                | 2008               | 8                  | auto(s6)           | r                  | 15                 | 25                 | p                  | 2seater            |\n",
       "| chevrolet          | corvette           | 7.0                | 2008               | 8                  | manual(m6)         | r                  | 15                 | 24                 | p                  | 2seater            |\n",
       "| chevrolet          | k1500 tahoe 4wd    | 5.3                | 2008               | 8                  | auto(l4)           | 4                  | 14                 | 19                 | r                  | suv                |\n",
       "| chevrolet          | k1500 tahoe 4wd    | 5.3                | 2008               | 8                  | auto(l4)           | 4                  | 11                 | 14                 | e                  | suv                |\n",
       "| ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... |\n",
       "| toyota            | toyota tacoma 4wd | 3.4               | 1999              | 6                 | auto(l4)          | 4                 | 15                | 19                | r                 | pickup            |\n",
       "| toyota            | toyota tacoma 4wd | 4.0               | 2008              | 6                 | manual(m6)        | 4                 | 15                | 18                | r                 | pickup            |\n",
       "| toyota            | toyota tacoma 4wd | 4.0               | 2008              | 6                 | auto(l5)          | 4                 | 16                | 20                | r                 | pickup            |\n",
       "| volkswagen        | gti               | 2.0               | 1999              | 4                 | manual(m5)        | f                 | 21                | 29                | r                 | compact           |\n",
       "| volkswagen        | gti               | 2.0               | 1999              | 4                 | auto(l4)          | f                 | 19                | 26                | r                 | compact           |\n",
       "| volkswagen        | gti               | 2.0               | 2008              | 4                 | manual(m6)        | f                 | 21                | 29                | p                 | compact           |\n",
       "| volkswagen        | gti               | 2.0               | 2008              | 4                 | auto(s6)          | f                 | 22                | 29                | p                 | compact           |\n",
       "| volkswagen        | gti               | 2.8               | 1999              | 6                 | manual(m5)        | f                 | 17                | 24                | r                 | compact           |\n",
       "| volkswagen        | jetta             | 1.9               | 1999              | 4                 | manual(m5)        | f                 | 33                | 44                | d                 | compact           |\n",
       "| volkswagen        | jetta             | 2.0               | 1999              | 4                 | manual(m5)        | f                 | 21                | 29                | r                 | compact           |\n",
       "| volkswagen        | jetta             | 2.0               | 1999              | 4                 | auto(l4)          | f                 | 19                | 26                | r                 | compact           |\n",
       "| volkswagen        | jetta             | 2.0               | 2008              | 4                 | auto(s6)          | f                 | 22                | 29                | p                 | compact           |\n",
       "| volkswagen        | jetta             | 2.0               | 2008              | 4                 | manual(m6)        | f                 | 21                | 29                | p                 | compact           |\n",
       "| volkswagen        | jetta             | 2.5               | 2008              | 5                 | auto(s6)          | f                 | 21                | 29                | r                 | compact           |\n",
       "| volkswagen        | jetta             | 2.5               | 2008              | 5                 | manual(m5)        | f                 | 21                | 29                | r                 | compact           |\n",
       "| volkswagen        | jetta             | 2.8               | 1999              | 6                 | auto(l4)          | f                 | 16                | 23                | r                 | compact           |\n",
       "| volkswagen        | jetta             | 2.8               | 1999              | 6                 | manual(m5)        | f                 | 17                | 24                | r                 | compact           |\n",
       "| volkswagen        | new beetle        | 1.9               | 1999              | 4                 | manual(m5)        | f                 | 35                | 44                | d                 | subcompact        |\n",
       "| volkswagen        | new beetle        | 1.9               | 1999              | 4                 | auto(l4)          | f                 | 29                | 41                | d                 | subcompact        |\n",
       "| volkswagen        | new beetle        | 2.0               | 1999              | 4                 | manual(m5)        | f                 | 21                | 29                | r                 | subcompact        |\n",
       "| volkswagen        | new beetle        | 2.0               | 1999              | 4                 | auto(l4)          | f                 | 19                | 26                | r                 | subcompact        |\n",
       "| volkswagen        | new beetle        | 2.5               | 2008              | 5                 | manual(m5)        | f                 | 20                | 28                | r                 | subcompact        |\n",
       "| volkswagen        | new beetle        | 2.5               | 2008              | 5                 | auto(s6)          | f                 | 20                | 29                | r                 | subcompact        |\n",
       "| volkswagen        | passat            | 1.8               | 1999              | 4                 | manual(m5)        | f                 | 21                | 29                | p                 | midsize           |\n",
       "| volkswagen        | passat            | 1.8               | 1999              | 4                 | auto(l5)          | f                 | 18                | 29                | p                 | midsize           |\n",
       "| volkswagen        | passat            | 2.0               | 2008              | 4                 | auto(s6)          | f                 | 19                | 28                | p                 | midsize           |\n",
       "| volkswagen        | passat            | 2.0               | 2008              | 4                 | manual(m6)        | f                 | 21                | 29                | p                 | midsize           |\n",
       "| volkswagen        | passat            | 2.8               | 1999              | 6                 | auto(l5)          | f                 | 16                | 26                | p                 | midsize           |\n",
       "| volkswagen        | passat            | 2.8               | 1999              | 6                 | manual(m5)        | f                 | 18                | 26                | p                 | midsize           |\n",
       "| volkswagen        | passat            | 3.6               | 2008              | 6                 | auto(s6)          | f                 | 17                | 26                | p                 | midsize           |\n",
       "\n"
      ],
      "text/plain": [
       "    manufacturer model              displ year cyl trans      drv cty hwy fl \n",
       "1   audi         a4                 1.8   1999 4   auto(l5)   f   18  29  p  \n",
       "2   audi         a4                 1.8   1999 4   manual(m5) f   21  29  p  \n",
       "3   audi         a4                 2.0   2008 4   manual(m6) f   20  31  p  \n",
       "4   audi         a4                 2.0   2008 4   auto(av)   f   21  30  p  \n",
       "5   audi         a4                 2.8   1999 6   auto(l5)   f   16  26  p  \n",
       "6   audi         a4                 2.8   1999 6   manual(m5) f   18  26  p  \n",
       "7   audi         a4                 3.1   2008 6   auto(av)   f   18  27  p  \n",
       "8   audi         a4 quattro         1.8   1999 4   manual(m5) 4   18  26  p  \n",
       "9   audi         a4 quattro         1.8   1999 4   auto(l5)   4   16  25  p  \n",
       "10  audi         a4 quattro         2.0   2008 4   manual(m6) 4   20  28  p  \n",
       "11  audi         a4 quattro         2.0   2008 4   auto(s6)   4   19  27  p  \n",
       "12  audi         a4 quattro         2.8   1999 6   auto(l5)   4   15  25  p  \n",
       "13  audi         a4 quattro         2.8   1999 6   manual(m5) 4   17  25  p  \n",
       "14  audi         a4 quattro         3.1   2008 6   auto(s6)   4   17  25  p  \n",
       "15  audi         a4 quattro         3.1   2008 6   manual(m6) 4   15  25  p  \n",
       "16  audi         a6 quattro         2.8   1999 6   auto(l5)   4   15  24  p  \n",
       "17  audi         a6 quattro         3.1   2008 6   auto(s6)   4   17  25  p  \n",
       "18  audi         a6 quattro         4.2   2008 8   auto(s6)   4   16  23  p  \n",
       "19  chevrolet    c1500 suburban 2wd 5.3   2008 8   auto(l4)   r   14  20  r  \n",
       "20  chevrolet    c1500 suburban 2wd 5.3   2008 8   auto(l4)   r   11  15  e  \n",
       "21  chevrolet    c1500 suburban 2wd 5.3   2008 8   auto(l4)   r   14  20  r  \n",
       "22  chevrolet    c1500 suburban 2wd 5.7   1999 8   auto(l4)   r   13  17  r  \n",
       "23  chevrolet    c1500 suburban 2wd 6.0   2008 8   auto(l4)   r   12  17  r  \n",
       "24  chevrolet    corvette           5.7   1999 8   manual(m6) r   16  26  p  \n",
       "25  chevrolet    corvette           5.7   1999 8   auto(l4)   r   15  23  p  \n",
       "26  chevrolet    corvette           6.2   2008 8   manual(m6) r   16  26  p  \n",
       "27  chevrolet    corvette           6.2   2008 8   auto(s6)   r   15  25  p  \n",
       "28  chevrolet    corvette           7.0   2008 8   manual(m6) r   15  24  p  \n",
       "29  chevrolet    k1500 tahoe 4wd    5.3   2008 8   auto(l4)   4   14  19  r  \n",
       "30  chevrolet    k1500 tahoe 4wd    5.3   2008 8   auto(l4)   4   11  14  e  \n",
       "... ...          ...                ...   ...  ... ...        ... ... ... ...\n",
       "205 toyota       toyota tacoma 4wd  3.4   1999 6   auto(l4)   4   15  19  r  \n",
       "206 toyota       toyota tacoma 4wd  4.0   2008 6   manual(m6) 4   15  18  r  \n",
       "207 toyota       toyota tacoma 4wd  4.0   2008 6   auto(l5)   4   16  20  r  \n",
       "208 volkswagen   gti                2.0   1999 4   manual(m5) f   21  29  r  \n",
       "209 volkswagen   gti                2.0   1999 4   auto(l4)   f   19  26  r  \n",
       "210 volkswagen   gti                2.0   2008 4   manual(m6) f   21  29  p  \n",
       "211 volkswagen   gti                2.0   2008 4   auto(s6)   f   22  29  p  \n",
       "212 volkswagen   gti                2.8   1999 6   manual(m5) f   17  24  r  \n",
       "213 volkswagen   jetta              1.9   1999 4   manual(m5) f   33  44  d  \n",
       "214 volkswagen   jetta              2.0   1999 4   manual(m5) f   21  29  r  \n",
       "215 volkswagen   jetta              2.0   1999 4   auto(l4)   f   19  26  r  \n",
       "216 volkswagen   jetta              2.0   2008 4   auto(s6)   f   22  29  p  \n",
       "217 volkswagen   jetta              2.0   2008 4   manual(m6) f   21  29  p  \n",
       "218 volkswagen   jetta              2.5   2008 5   auto(s6)   f   21  29  r  \n",
       "219 volkswagen   jetta              2.5   2008 5   manual(m5) f   21  29  r  \n",
       "220 volkswagen   jetta              2.8   1999 6   auto(l4)   f   16  23  r  \n",
       "221 volkswagen   jetta              2.8   1999 6   manual(m5) f   17  24  r  \n",
       "222 volkswagen   new beetle         1.9   1999 4   manual(m5) f   35  44  d  \n",
       "223 volkswagen   new beetle         1.9   1999 4   auto(l4)   f   29  41  d  \n",
       "224 volkswagen   new beetle         2.0   1999 4   manual(m5) f   21  29  r  \n",
       "225 volkswagen   new beetle         2.0   1999 4   auto(l4)   f   19  26  r  \n",
       "226 volkswagen   new beetle         2.5   2008 5   manual(m5) f   20  28  r  \n",
       "227 volkswagen   new beetle         2.5   2008 5   auto(s6)   f   20  29  r  \n",
       "228 volkswagen   passat             1.8   1999 4   manual(m5) f   21  29  p  \n",
       "229 volkswagen   passat             1.8   1999 4   auto(l5)   f   18  29  p  \n",
       "230 volkswagen   passat             2.0   2008 4   auto(s6)   f   19  28  p  \n",
       "231 volkswagen   passat             2.0   2008 4   manual(m6) f   21  29  p  \n",
       "232 volkswagen   passat             2.8   1999 6   auto(l5)   f   16  26  p  \n",
       "233 volkswagen   passat             2.8   1999 6   manual(m5) f   18  26  p  \n",
       "234 volkswagen   passat             3.6   2008 6   auto(s6)   f   17  26  p  \n",
       "    class     \n",
       "1   compact   \n",
       "2   compact   \n",
       "3   compact   \n",
       "4   compact   \n",
       "5   compact   \n",
       "6   compact   \n",
       "7   compact   \n",
       "8   compact   \n",
       "9   compact   \n",
       "10  compact   \n",
       "11  compact   \n",
       "12  compact   \n",
       "13  compact   \n",
       "14  compact   \n",
       "15  compact   \n",
       "16  midsize   \n",
       "17  midsize   \n",
       "18  midsize   \n",
       "19  suv       \n",
       "20  suv       \n",
       "21  suv       \n",
       "22  suv       \n",
       "23  suv       \n",
       "24  2seater   \n",
       "25  2seater   \n",
       "26  2seater   \n",
       "27  2seater   \n",
       "28  2seater   \n",
       "29  suv       \n",
       "30  suv       \n",
       "... ...       \n",
       "205 pickup    \n",
       "206 pickup    \n",
       "207 pickup    \n",
       "208 compact   \n",
       "209 compact   \n",
       "210 compact   \n",
       "211 compact   \n",
       "212 compact   \n",
       "213 compact   \n",
       "214 compact   \n",
       "215 compact   \n",
       "216 compact   \n",
       "217 compact   \n",
       "218 compact   \n",
       "219 compact   \n",
       "220 compact   \n",
       "221 compact   \n",
       "222 subcompact\n",
       "223 subcompact\n",
       "224 subcompact\n",
       "225 subcompact\n",
       "226 subcompact\n",
       "227 subcompact\n",
       "228 midsize   \n",
       "229 midsize   \n",
       "230 midsize   \n",
       "231 midsize   \n",
       "232 midsize   \n",
       "233 midsize   \n",
       "234 midsize   "
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "show_missings(mpg)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 94,
   "metadata": {},
   "outputs": [],
   "source": [
    "show_missings = function(df) {\n",
    "  n <- sum(is.na(df))\n",
    "  cat(\"Missing values: \", n, \"\\n\", sep = \"\")\n",
    "  invisible(df)  # return will not print out\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 99,
   "metadata": {},
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "Warning message:\n",
      "\"package 'nycflights13' was built under R version 3.6.3\""
     ]
    }
   ],
   "source": [
    "library(nycflights13)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 100,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Missing values: 46595\n"
     ]
    }
   ],
   "source": [
    "show_missings(flights)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 101,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Missing values: 18387\n"
     ]
    }
   ],
   "source": [
    "flights %>% filter(month < 5) %>% show_missings"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Local vs Global Variables"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "https://www.w3chools.com/r/r_variables_global.asp#:~:text=If%20you%20create%20a%20variable,and%20with%20the%20original%20value."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
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  "kernelspec": {
   "display_name": "R",
   "language": "R",
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  },
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   "codemirror_mode": "r",
   "file_extension": ".r",
   "mimetype": "text/x-r-source",
   "name": "R",
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