Let's make something interactive! Start off by installing the shiny package:
install.packages("shiny")
And then downloading this file:
- Shiny is an R package that makes it easy to build interactive web apps.
- Shiny apps are interactive ways to display/showcase or work with your data. See here: https://shiny.rstudio.com/
- Reactivity is the ability of a program to compute outputs from user inputs
- The program 'responds' to user defined changes
- Three components:
- Reactive Inputs
- Triggers that cause values to be set in the environment
- actions from buttons, selections, uploads, forms, etc.
- Reactive Outputs
- Outputs displayed on the browser
- graphs, plots, tables, etc.
- Reactive Expressions
- expressions that take in the reactive input and convert it to a reactive output
- User interface function (
ui
) defines the structure of the page - Placing a function in ui tells shiny where to display your object
- Add an R object to your user interface, the object will be reactive if the code that builds it calls a widget value
- a widget is a web element that your users can interact with
ui <- fluidPage(
titlePanel("This is the title"),
# Inputs
sidebarLayout(
sidebarPanel(
textInput("one", "Number1"),
textInput("two", "Number2"),
textInput("caption", "Text1"),
actionButton("add", "Add"),
checkboxInput(inputId = "obs", label = strong("Show individual observations"), value = FALSE),
sliderInput("bins", "Number of bins:", min = 1, max = 10, value = 5)
),
# Result display
mainPanel(
textOutput("check"),
plotOutput("distPlot"),
tableOutput("table")
)
)
)
- The server function (
server
), where all the action happens - Where you tell shiny how to build your objects
- it builds a list named
output
that contains all of the code needed to update the R objects in your app - Note, each R object needs to have its own entry in the list, and you do so by "defining" the element. Each ouput element needs to be matched to its input element in the ui.
. E.g., element "check":
--
output$check
inserver
matchestextOutput("check")
inui
server <- function(input,output,session) {
# Reactive input
observeEvent( input$add,{
x <- as.numeric(input$one)
y <- as.numeric(input$two)
title <- as.character(input$caption)
# Reactive expressions
n <- x+y
d <- round(abs(rnorm(n) ) * n )
m <- mean(d)
sdd <- sd(d)
bins <- seq(min(d), max(d), length.out = input$bins + 1)
# Reactive output
output$check <- renderPrint("Done!")
output$distPlot <- renderPlot({
# Draw the histogram with the specified number of bins
hist(d, breaks = bins, freq=F, col = 'darkgray', border = 'white', main=title)
ld <- density(d)
lines(ld, col=4)
abline(v=m, lty=2, lwd=3, col=4)
if (input$obs) { rug(d) }
})
output$table <- renderTable({
data = cbind(n,m, sdd)
return( data )
})
})
)
shinyApp(ui = ui, server = server)
- go in the ui function
function | widget |
---|---|
actionButton | Action Button |
checkboxGroupInput | A group of check boxes |
checkboxInput | A single check box |
dateInput | A calendar to aid date selection |
dateRangeInput | A pair of calendars for selecting a date range |
fileInput | A file upload control wizard |
helpText | Help text that can be added to an input form |
numericInput | A field to enter numbers |
radioButtons | A set of radio buttons |
selectInput | A box with choices to select from |
sliderInput | A slider bar |
submitButton | A submit button |
textInput | A field to enter text |
- go in the ui function
Output function | Creates |
---|---|
dataTableOutput | DataTable |
htmlOutput | raw HTML |
imageOutput | image |
plotOutput | plot |
ableOutput | table |
textOutput | text |
uiOutput | raw HTML |
verbatimTextOutput | text |
- go in the server function
render function | Creates |
---|---|
renderDataTable | DataTable |
renderImage | images (saved as a link to a source file) |
renderPlot | plots |
renderPrint | any printed output |
renderTable | data frame, matrix, other table like structures |
renderText | character strings |
renderUI | a Shiny tag object or HTML |
- Install it!
install.packages("shiny")
- Load it!
library(shiny)
- RStudio makes it very easy to build an app. Simply click on the "File" dropdown menu, then "New File" and then "Shiny Web App...". A pop up box will ask you for an "Application name", call your app whatever you wish (e.g., my_app). Select the "Single File (app.R)" radio button. And then pick your working directory (click Browse on the final box). When you are ready, click "Create".
- This will generate a folder with your app name, and a file called "app.R". We will be working with this file. It should have two functions: ui and server. They should be pre-filled with a historgram drawing app. You can test it out by running in the command console (make sure you are in the working directory where your app is):
runApp("my_app")
-
We can modify the different bits of code in the ui and server functions to change the display and functionality of the code.
-
Play around!
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