What do you think about @groupby ?

[flyaflya]

I am a big fan of Hadley Wickham's pit of success where it is easy to remember how to do things. I find the fact that groupby is the only non-macro getting used in a typical DataFramesMeta workflow creates mental friction for new users (and me). Wouldn't it be nice if the below table could have the @ symbol in front of group by? Can an alias be made?

[pdeffebach]

Thanks for filing the issue!

I don't think it's worth adding a macro just for the sake of consistency with @. It seems redundant to have a @ which doesn't do anything different. But if there is large community interest for this I may reconsider the importance of easy-to-rememberness.

This was actually a major benefit of the now-deprecated @linq, which allowed omitting the @ for macro names.

DataFrameMacros.jl has a @groupby macro which is used to construct groups on the fly, which also copies a data frame.

I want to emulate this behavior but I want to call it something different. DataFrames.groupby does not allocate a new data frame, wheras @groupby from DataFramesMeta.jl does, and I don't like deviating from DataFrames.jl too much.

One alternative would be to have a @makegroups macro which performs a transformation and returns a grouped data frame. I thought I had an issue mentioning this, but I can't find it.

[flyaflya]

Thx for the quick reply and the consideration. I am coming from rstats tidyverse where it seems everything is conceptually so much easier to accomplish than their counterparts in Julia; the Julia syntax and typing is a lot of mental overhead. Your package is an exception though - it is exceptionally easy to use! Thank you! For example, the @rfoo macros are just a tremendous addition to easy-to-code data manipulation pipelines.

Anyway, anything leading to easy-to-rememberness is very welcomed by me and this pattern-breaking by groupby just makes my brain twitch a little bit. In the R tidyverse-world, I am confident they would add this alias. Functions like is.character() in base get rewritten as is_character() in the tidyverse so that the syntax is the same as tidyverse-only functions like is_dictionaryish() or is_scalar_vector().

I hope some community members might chime in and agree, but either way thx for the great package.

[bkamins]

I would have no problem with adding @groupby. The issue is - as @pdeffebach commented that ideally it should allow transforms, but then it would have to make a copy.

[nalimilan]

I agree that it could make sense to add the macro just for consistency, even if it's identical to the function.

[pdeffebach]

Sounds good. I can start a PR adding this.

[flyaflya]

Great! Please know that I am not clear on the "transforms" issue above, so can't comment on that. That being said, identical functionality to groupby sounds good to me.

[bkamins]

"transforms" issue above

You might want to groupby not by columns directly but by their transformations (e.g. you have a columns of integers and you want to groupby the fact if the value is even or odd)

[pdeffebach]

I had a good idea this week for more features, something like

df = @groubby df :a begin 
    @transform :y = :x .- mean(:x)
    @combine :z = first(:y)
end

where the operations inside the @groupby block are transform(df, ...; ungroup = false), so you can do a lot of grouped transformations together.

This is partly a hack because we still don't have a syntax for keyword arguments, so you can't have ungroup = false in the @transform call.

I don't think this means we can't introduce a @groupby which only accepts a few things right now though.

[pdeffebach]

Added @groupby in [#373] (did not add the feature above though. We now have keyword arguments in #323)