Added spearmanr

[sleighsoft]

Addresses issue lmcinnes/umap#319 and #85

I know tests are missing, but I am not 100% sure how to add them the right way. Guidance welcome.

[lmcinnes]

Thanks, this looks promising. For tests I think the custom distances require just testing things independently. You can probably just write a couple of tests, one that verifies that the ranking function works as intended, and one that just tests that the spearman distance outputs the results you would expect for some reasonable test vectors (a random example, and a few corner cases such as all 0 vectors, etc.)

[gokceneraslan]

Cool! Can you also check if all numpy calls are supported by numba's numpy support: https://numba.pydata.org/numba-doc/dev/reference/numpysupported.html

[lmcinnes]

Ideally this will happen once some tests exercise that code -- and then we can fix up any issues.

[sleighsoft]

I have this working in a jupyter notebook. So it is definitely numba compatible.
Will add tests in the upcoming days.

[sleighsoft]

Tests added.

[lmcinnes]

It looks like it is just black formatting holding up the tests right now.

[sleighsoft]

Weird, I ran black on all of them. + I did not modify rp_trees and _threaded

[lmcinnes]

I'm not really sure what the issue is; I'll just merge this and then deal with the fall-out from there. Thanks for submitting this!