5.6 Data Summaries

Similar to the combine DataFrames.jl function (Section 4.8), DataFramesMeta.jl has a @combine macro.

1. @combine leftjoined :mean_grade_2020 = mean(:grade_2020)

@combine also supports multiple operations inside a begin ... end statement:

1. @combine leftjoined begin
2. :mean_grade_2020 = mean(:grade_2020)
3. :mean_grade_2021 = mean(:grade_2021)
4. end

Most of the time we would use @combine in a grouped dataframe by pairing it with groupby:

1. gdf = groupby(leftjoined, :name)
2. @combine gdf begin
3. :mean_grade_2020 = mean(:grade_2020)
4. :mean_grade_2021 = mean(:grade_2021)
5. end

Support this project CC BY-NC-SA 4.0 Jose Storopoli, Rik Huijzer, Lazaro Alonso