Feature request: Other correlation metrics #319

https://github.com/lmcinnes/umap/issues/319

@gokceneraslan

It'd be great to add other correlations as distances, such as Spearman's rho or the new correlation coefficient called phi_k. I am aware that it's possible to use any distance metric using either metric='precomputed' or implementing a custom function, but it'd be more convenient to pass metric='spearmanrho' or 'phik' directly.

Start by locating the code that handles the metric argument and existing distance metrics; inspect how metric='precomputed' and custom functions are supported. Find the tests covering metric selection, then define done as accepting the requested Spearman rho and phi_k metric names directly with matching distance behavior.

Written by the indexing model from the issue text.