Consider
using DataFrames
df=DataFrame(a=1:3, b=1:3, c=1:3)
and suppose I want to turn Between(:b, :c) into column indices, which should return [2, 3]?
I can select those columns extract the names and then call columnindex but that's not very elegant.
Use:
names(df, Between(:b, :c))
to get the selected column names and:
columnindex.(Ref(df), names(df, Between(:b, :c)))
or (a longer but easier to read)
[columnindex(df, n) for n in names(df, Between(:b, :c))]
to get column numbers.
If you wanted something faster that is internal (i.e. not guaranteed to be working in the long term and not documented; though it it unlikely to be changed - so it is relatively safe to use):
DataFrames.index(df)[Between(:b, :c)]
A small difference between getindex on DataFrames.index and using columnindex is that:
columnindex will return 0 for non-existent column (while getindex on DataFrames.index errors)columnindex, while you can pass it to getindex on DataFrames.index