Better Grouping With dplyr

John Mount builds a function to improve upon the group-by to mutate model in dplyr:

The advantages of the shorthand are:

• The analyst only has to specify the grouping column once.
• The data (mtcars) enters the pipeline only once.
• The analyst doesn’t have to start thinking about joins immediately.

Frankly I’ve never liked the shorthand. I feel it is a “magic extra” that a new user would have no way of anticipating from common use of group_by() and summarize(). I very much like the idea of wrapping this important common use case into a single verb. Adjoining “windowed” or group-calculated columns is a common and important step in analysis, and well worth having its own verb.

Below is our attempt at elevating this pattern into a packaged verb.

Click through for the script.  I’d like to see something like this make its way into dplyr.