Creating a 3d frequency array for categorical variables from a dataframe

New to Julia
4

Ah yes I see now.

This is is a commonly requested feature in DataFrames. There is no way to index columns for an easy lookup like that.

You can make a GroupedDataFrame grouping on [:a, :b, :c] and then index like

gd[(a = 1, b = 2, c = 3)]

This will be fast since a GroupedDataFrame creates a hash for lookup just like a Dict.

However this will return a SubDataFrame, which is itself not the nicest object.

I would do the following

julia> gd = groupby(df_fraction, [:a, :b, :c]);

julia> function get_fraction(gd, ;a = nothing, b = nothing, c = nothing)
           only(gd[(;a, b, c)]).fraction
       end
get_fraction (generic function with 1 method)

julia> get_fraction(gd; a = 1, b = 2, c = 3)
0.018
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