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README.md

An Introduction to DataFrames

Bogumił Kamiński, May 6, 2020

The tutorial is for DataFrames 0.21.0

A brief introduction to basic usage of DataFrames.

The tutorial contains a specification of the project environment version under which it should be run. In order to prepare this environment, before using the tutorial notebooks, while in the project folder run the following command in the command line:

julia -e 'using Pkg; Pkg.activate("."); Pkg.instantiate()'

Tested under Julia 1.4.1. The project dependencies are the following:

  [6e4b80f9] BenchmarkTools v0.5.0
  [336ed68f] CSV v0.6.2
  [5d742f6a] CSVFiles v1.0.0
  [324d7699] CategoricalArrays v0.8.0
  [944b1d66] CodecZlib v0.6.0
  [a93c6f00] DataFrames v0.21.0
  [1313f7d8] DataFramesMeta v0.5.1
  [becb17da] Feather v0.5.6
  [5789e2e9] FileIO v1.3.0
  [da1fdf0e] FreqTables v0.3.3
  [7073ff75] IJulia v1.21.2
  [babc3d20] JDF v0.2.15
  [9da8a3cd] JLSO v2.3.2
  [b9914132] JSONTables v1.0.0
  [86f7a689] NamedArrays v0.9.4
  [b98c9c47] Pipe v1.2.0
  [2dfb63ee] PooledArrays v0.5.3
  [f3b207a7] StatsPlots v0.14.5
  [bd369af6] Tables v1.0.4
  [a5390f91] ZipFile v0.9.1
  [9a3f8284] Random
  [10745b16] Statistics

I will try to keep the material up to date as the packages evolve.

This tutorial covers DataFrames and CategoricalArrays, as they constitute the core of DataFrames along with selected file reading and writing packages.

In the last extras part mentions selected functionalities of selected useful packages that I find useful for data manipulation, currently those are: FreqTables, DataFramesMeta, StatsPlots.

Setting up Jupyter Notebook for work with DataFrames.jl

By default Jupyter Notebook will limit the number of rows and columns when displaying a data frame to roughly fit the screen size (like in the REPL).

You can override this behavior by setting ENV["COLUMNS"] or ENV["LINES"] variables to hold the maximum width and height of output in characters respectively when running a notebook. Alternatively you can add the following entry "COLUMNS": "1000", "LINES": "100" to "env" variable in your Jupyter kernel file. See here for information about location and specification of Jupyter kernels.

TOC

File Topic
01_constructors.ipynb Creating DataFrame and conversion
02_basicinfo.ipynb Getting summary information
03_missingvalues.ipynb Handling missing values
04_loadsave.ipynb Loading and saving DataFrames
05_columns.ipynb Working with columns of DataFrame
06_rows.ipynb Working with row of DataFrame
07_factors.ipynb Working with categorical data
08_joins.ipynb Joining DataFrames
09_reshaping.ipynb Reshaping DataFrames
10_transforms.ipynb Transforming DataFrames
11_performance.ipynb Performance tips
12_pitfalls.ipynb Possible pitfalls
13_extras.ipynb Additional interesting packages

Changelog:

Date Changes
2017-12-05 Initial release
2017-12-06 Added description of insert!, merge!, empty!, categorical!, delete!, DataFrames.index
2017-12-09 Added performance tips
2017-12-10 Added pitfalls
2017-12-18 Added additional worthwhile packages: FreqTables and DataFramesMeta
2017-12-29 Added description of filter and filter!
2017-12-31 Added description of conversion to Matrix
2018-04-06 Added example of extracting a row from a DataFrame
2018-04-21 Major update of whole tutorial
2018-05-01 Added byrow! example
2018-05-13 Added StatPlots package to extras
2018-05-23 Improved comments in sections 1 do 5 by Jane Herriman
2018-07-25 Update to 0.11.7 release
2018-08-25 Update to Julia 1.0 release: sections 1 to 10
2018-08-29 Update to Julia 1.0 release: sections 11, 12 and 13
2018-09-05 Update to Julia 1.0 release: FreqTables section
2018-09-10 Added CSVFiles section to chapter on load/save
2018-09-26 Updated to DataFrames 0.14.0
2018-10-04 Updated to DataFrames 0.14.1, added haskey and repeat
2018-12-08 Updated to DataFrames 0.15.2
2019-01-03 Updated to DataFrames 0.16.0, added serialization instructions
2019-01-18 Updated to DataFrames 0.17.0, added passmissing
2019-01-27 Added Feather.jl file read/write
2019-01-30 Renamed StatPlots.jl to StatsPlots.jl and added Tables.jl
2019-02-08 Added groupvars and groupindices functions
2019-04-27 Updated to DataFrames 0.18.0, dropped JLD2.jl
2019-04-30 Updated handling of missing values description
2019-07-16 Updated to DataFrames 0.19.0
2019-08-14 Added JSONTables.jl and Tables.columnindex
2019-08-16 Added Project.toml and Manifest.toml
2019-08-26 Update to Julia 1.2 and DataFrames 0.19.3
2019-08-29 Add example how to compress/decompress CSV file using CodecZlib
2019-08-30 Add examples of JLSO.jl and ZipFile.jl by xiaodaigh
2019-11-03 Add examples of JDF.jl by xiaodaigh
2019-12-08 Updated to DataFrames 0.20.0
2020-05-06 Updated to DataFrames 0.21.0 (except load/save and extras)

Core functions summary

  1. Constructors: DataFrame, DataFrame!, Tables.rowtable, Tables.columntable, Matrix, eachcol, eachrow, Tables.namedtupleiterator
  2. Getting summary: size, nrow, ncol, describe, names, eltypes, first, last, getindex, setindex!, @view
  3. Handling missing: missing (singleton instance of Missing), ismissing, nonmissingtype, skipmissing, replace, replace!, coalesce, allowmissing, disallowmissing, allowmissing!, completecases, dropmissing, dropmissing!, disallowmissing, disallowmissing!, passmissing
  4. Loading and saving: CSV (package), CSVFiles (package), Serialization (module), CSV.read, CSV.write, save, load, serialize, deserialize, Feather.write, Feather.read, Feather.materialize (from Feather package), JSONTables (package), arraytable, objecttable, jsontable, CodecZlib (module), GzipCompressorStream, GzipDecompressorStream, JDF.jl (package), JDF.savejdf, JDF.loadjdf, JLSO.jl (package), JLSO.save, JLSO.load, ZipFile.jl (package), ZipFile.reader, ZipFile.writer, ZipFile.addfile
  5. Working with columns: rename, rename!, hcat, insertcols!, categorical!, columnindex, hasproperty, select, select!, transform, transform!, combine, Not, All, Between, ByRow, AsTable
  6. Working with rows: sort!, sort, issorted, append!, vcat, push!, view, filter, filter!, delete!, unique, nonunique, unique!, repeat, parent, parentindices, flatten, @pipe (from Pipe package)
  7. Working with categorical: categorical, cut, isordered, ordered!, levels, unique, levels!, droplevels!, get, recode, recode!
  8. Joining: innerjoin, leftjoin, rightjoin, outerjoin, semijoin, antijoin, crossjoin
  9. Reshaping: stack, unstack
  10. Transforming: groupby, mapcols, parent, groupcols, valuecols, groupindices, keys (for GroupedDataFrame), combine, select, select!, transform, transform!, @pipe (from Pipe package)
  11. Extras:
    • FreqTables: freqtable, prop, Name
    • DataFramesMeta: @with, @where, @select, @transform, @orderby, @linq, by, based_on, byrow!
    • StatsPlots: @df, plot, density, histogram,boxplot, violin
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