Feature Request: Ordered Samples in plot_richness

[zachcp]

Hi Joey711,

I have a small feature request: allowing ordering when plotting richness. In my use-case I often have many samples and it would be visually cleaner to be able to order the x-axis position of the samples to give the cleanest look. In this case sorting by the number of observed OTUS would generate a more interpretable graph. You could also imagine sorting the x-axis by some other grouping variable.

Would you have any interest in implementing this feature? There are a nubmer of examples on how to do this: here and here, for example. I would be happy to take a stab at it if you like.

thanks,
zach cp

[joey711]

Done!

I changed the spec a bit after looking into it. Sorry for the stray errand. The sample_variables suggestion was totally irrelevant, because the x-axis is mapped according to an explicit x argument. To make it work and make sense I expanded on the parts regarding the alpha-measure sorting, but included a couple checks that ensure that x-axis is mapped to a discrete variable (sorting wouldn't make sense if x is mapped to some continuous observation on samples), and also that sortby is among the included measures arguments. Also updated in the documentation and tests. Let me know if you find any deficiencies. It definitely does what you originally requested, plus some added flexibility with measures. Cool suggestion, and thanks for the pull!

joey