Mean of windowed popgen stats

Currently the windowed aggregation of statistics in popgen.py is hard-coded to use np.sum [1, 2, 3, 4]. Would it be possible to make this aggregation optional or have a span_normalise argument as in Tskit?

Another option would be to record the number of loci in each window so that the user can manual average the sums. Or to return both a stat_sum and stat_mean variable by default.

[tomwhite]

Just a thought, would it be worth adding window_base_start and window_base_stop instead?

Yes, that’s better. Perhaps window_start_position and window_stop_position to echo the variant_position variable?

This will take us into coordinate system territory (#434). (I realised the code I posted also needs to clip start positions to be at least 0 or 1, depending on the coordinate system in use.)

[timothymillar]

Should the window functions add a window_base_length variable?

Just a thought, would it be worth adding window_base_start and window_base_stop instead? That would allow a more direct translation to and from BED, GFF and etc in future, if that’s useful?