Weighted aggregated_by

[schlunma]

✨ Feature Request

Similar to iris.cube.Cube.collapsed, it would be nice if iris.cube.Cube.aggregated_by could also support weights.

Motivation

iris.cube.Cube.aggregated_by currently does not support weights. Using weights in aggregated_by might be helpful in lots of use cases, e.g., when calculating annual means for monthly data where the months have a different number of days.

Additional context

I tried to implement this for the non-lazy case (see this commit). It actually doesn't require a lot of changes. If you think this feature is helpful, I can come up with a solution for the lazy case and open a pull request.

Thanks!!

[rcomer]

This has been requested before - #3290, so seems like a good idea to me. There was talk in that issue of rationalising some of the collapsed/aggregated_by code though, which would have made it a bigger task I guess.