v0.21.1

DataFrames v0.21.1

Diff since v0.21.0

Closed issues:

• Standardizing working with multiple columns (#2016)
• In docs, note subsets are copies (unless of columns)? (#2224)
• first/last/etc. documentation problem (#2232)
• Make DataFrame's BoundsError message more informative and similar to that of Base.Matrix (#2234)
• Problems in groupreduce_init (#2241)
• Tables.columns should return a DataFrameColumns object (#2244)
• map on DataFrameColumns should return DataFrameColumns (#2245)
• rename(uppercase, df) doesn't work anymore (#2252)
• update docs at pkg.julialang.org (#2255)
• allow [:a,:b,:c,:d] => fun => new_column_name syntax (#2256)
• ENV["COLUMNS"] not working as expected in Jupyter Lab (#2266)

Merged pull requests:

• add note on views / copies in getting started -- #2224 (#2226) (@nickeubank)
• Fix several references in documentation (#2231) (@dmolina)
• Fix docstring references in the manual (#2233) (@mortenpi)
• better deprecations of by and map (#2249) (@bkamins)
• fix bug in reduceinit (#2263) (@bkamins)