Low level pair coalescence rates

[nspope]

Low level pair coalescence rates within time windows, followup to #2976

[codecov]

Codecov Report

Attention: Patch coverage is 98.91304% with 2 lines in your changes missing coverage. Please review.

Project coverage is 89.71%. Comparing base (46578bd) to head (2bc7118).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
python/_tskitmodule.c	97.50%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2985      +/-   ##
==========================================
+ Coverage   89.65%   89.71%   +0.05%     
==========================================
  Files          29       29              
  Lines       31116    31298     +182     
  Branches     6031     6067      +36     
==========================================
+ Hits        27898    28078     +180     
- Misses       1836     1837       +1     
- Partials     1382     1383       +1     

Flag	Coverage Δ
c-tests	86.46% <100.00%> (+0.06%)	⬆️
lwt-tests	80.78% <ø> (ø)
python-c-tests	88.98% <97.50%> (+0.09%)	⬆️
python-tests	99.01% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
c/tskit/core.c	95.83% <100.00%> (+0.07%)	⬆️
c/tskit/core.h	100.00% <ø> (ø)
c/tskit/trees.c	90.44% <100.00%> (+0.11%)	⬆️
python/tskit/trees.py	98.78% <100.00%> (+0.01%)	⬆️
python/_tskitmodule.c	88.98% <97.50%> (+0.09%)	⬆️

[nspope]

Hey @jeromekelleher this is ready to be merged after a review. Thanks!

One question is what the output fill value should be for time windows that do not contain any nodes. I'm filling these with NaN at the moment, but zero also makes sense in this particular context. Maybe it should match what will be done for other time-windowed statistics (@petrelharp and @tforest have you decided on this?)

[jeromekelleher]

Super! Merging

[jeromekelleher]

Just to note we have tsk_search_sorted if you want to try it out