Minimum cell cutoff in sc.pl.dotplot

• Additional function parameters / changed functionality / changed defaults?
• New analysis tool: A simple analysis tool you have been using and are missing in sc.tools?
• New plotting function: A kind of plot you would like to seein sc.pl?
• External tools: Do you know an existing package that should go into sc.external.*?
• Other?

Especially when we visualize large datasets with multiple categorical variables (e.g. patient, disease, cell type) using sc.pl.dotplot, and we use a sequence in the groupby argument (e.g. sc.pl.dotplot(ad, 'genex', groupby=['individual', 'disease_status', 'cell type'])), sometimes we end up with too few cells in some rows, in which summary statistics like fraction of nonzero expressors or mean expression are not very robust.

To avoid that, I think it'd be cool to have a minimum observation cutoff in the function, where e.g. min_cells=5 would show groupby combinations with at least 5 cells. Without this option, this sort of filtering becomes an annoying pandas exercise (which some might enjoy but possibly not everyone).

Start at the sc.pl.dotplot entry point and inspect how combinations from a sequence of groupby variables are formed and displayed. Add a minimum-cell cutoff such as min_cells=5, then verify that combinations below the threshold are excluded while valid combinations remain visible and their summary statistics are calculated.