Julia DataFrames: How to efficiently convert column data and column name to uppercase/lowercase at o-CodePudding

I have a DataFrame that looks like this:

5×4 DataFrame
 Row │ Col_1      Col_2     Col_a   Col_z  
     │ Float64    Float64   String  String 
─────┼─────────────────────────────────────
   1 │ 0.201256   0.418266  aabbcc  xxyyzz
   2 │ 0.804066   0.136453  aabbcc  xxyyzz
   3 │ 0.442338   0.305655  aabbcc  xxyyzz
   4 │ 0.0676846  0.113499  aabbcc  xxyyzz
   5 │ 0.380939   0.773559  aabbcc  xxyyzz

but with many String columns. What is an efficient (and preferably one-liner) solution to convert both column data and column names to uppercase for only these columns? So to get something like:

5×4 DataFrame
 Row │ Col_1      Col_2     COL_A   COL_Z  
     │ Float64    Float64   String  String 
─────┼─────────────────────────────────────
   1 │ 0.201256   0.418266  AABBCC  XXYYZZ
   2 │ 0.804066   0.136453  AABBCC  XXYYZZ
   3 │ 0.442338   0.305655  AABBCC  XXYYZZ
   4 │ 0.0676846  0.113499  AABBCC  XXYYZZ
   5 │ 0.380939   0.773559  AABBCC  XXYYZZ

CodePudding user response：

if df is your data frame there tare two options.

If you do not need to keep the column order

select(df, Not(names(df, AbstractString)), names(df, AbstractString) .=> ByRow(uppercase) .=> uppercase)

If you need to keep the column order:

select(df, [n => eltype(v) <: AbstractString ? ByRow(uppercase) => uppercase : n for  (n, v) in  pairs(eachcol(df))])

(both solutions assume you do not have missing values in your data as in your question)