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DataFrames v0.22 Release Notes

Breaking changes

  • the rules for transformations passed to select/select!, transform/transform!, and combine have been made more flexible; in particular now it is allowed to return multiple columns from a transformation function (#2461 and #2481)
  • CategoricalArrays.jl is no longer reexported: call using CategoricalArrays to use it #2404. In the same vein, the categorical and categorical! functions have been deprecated in favor of transform(df, cols .=> categorical .=> cols) and similar syntaxes #2394. stack now creates a PooledVector{String} variable column rather than a CategoricalVector{String} column by default; pass variable_eltype=CategoricalValue{String} to get the previous behavior (#2391)
  • isless for DataFrameRows now checks column names (#2292)
  • DataFrameColumns is now not a subtype of AbstractVector (#2291)
  • nunique is not reported now by describe by default (#2339)
  • stop reordering columns of the parent in transform and transform!; always generate columns that were specified to be computed even for GroupedDataFrame with zero rows (#2324)
  • improve the rule for automatically generated column names in combine/select(!)/transform(!) with composed functions (#2274)
  • :nmissing in describe now produces 0 if the column does not allow missing values; earlier nothing was produced in this case (#2360)
  • fast aggregation functions in for GroupedDataFrame now correctly choose the fast path only when it is safe; this resolves inconsistencies with what the same functions not using fast path produce (#2357)
  • joins now return PooledVector not CategoricalVector in indicator column (#2505)
  • GroupKeys now supports in for GroupKey, Tuple, NamedTuple and dictionaries (2392)
  • in describe the specification of custom aggregation is now function => name; old name => function order is now deprecated (#2401)
  • in joins passing NaN or real or imaginary -0.0 in on column now throws an error; passing missing thows an error unless matchmissing=:equal keyword argument is passed (#2504)
  • unstack now produces row and column keys in the order of their first appearance and has two new keyword arguments allowmissing and allowduplicates (#2494)
  • PrettyTables.jl is now the default back-end to print DataFrames to text/plain; the print option splitcols was removed and the output format was changed (#2429)

New functionalities

  • add filter to GroupedDataFrame (#2279)
  • add empty and empty! function for DataFrame that remove all rows from it, but keep columns (#2262)
  • make indicator keyword argument in joins allow passing a string (#2284, #2296)
  • add new functions to GroupKey API to make it more consistent with DataFrameRow (#2308)
  • allow column renaming in joins (#2313 and (#2398)
  • add rownumber to DataFrameRow (#2356)
  • allow passing column name to specify the position where a new columns should be inserted in insertcols! (#2365)
  • allow GroupedDataFrames to be indexed using a dictionary, which can use Symbol or string keys and are not dependent on the order of keys. (#2281)
  • add isapprox method to check for approximate equality between two dataframes (#2373)
  • add columnindex for DataFrameRow (#2380)
  • names now accepts Type as a column selector (#2400)
  • select, select!, transform, transform! and combine now allow renamecols keyword argument that makes it possible to avoid adding transformation function name as a suffix in automatically generated column names (#2397)
  • filter, sort, dropmissing, and unique now support a view keyword argument which if set to true makes them retun a SubDataFrame view into the passed data frame.
  • add only method for AbstractDataFrame (#2449)
  • passing empty sets of columns in filter/filter! and in select/transform/combine with ByRow is now accepted (#2476)
  • add permutedims method for AbstractDataFrame (#2447)
  • add support for Cols from DataAPI.jl (#2495)

Deprecated

  • DataFrame! is now deprecated (#2338)
  • several in-standard DataFrame constructors are now deprecated (#2464)
  • all old deprecations now throw an error (#2350)

Dependency changes

  • Tables.jl version 1.2 is now required.
  • DataAPI.jl version 1.4 is now required. It implies that All(args...) is deprecated and Cols(args...) is recommended instead. All() is still supported.

Other relevant changes

  • Documentation is now available also in Dark mode (#2315)
  • add rich display support for Markdown cell entries in HTML and LaTeX (#2346)
  • limit the maximal display width the output can use in text/plain before being truncated (in the textwidth sense, excluding …) to 32 per column by default and fix a corner case when no columns are printed in situations when they are too wide (#2403)
  • Common methods are now precompiled to improve responsiveness the first time a method is called in a Julia session. Precompilation takes up to 30 seconds after installing the package (#2456).