Join count tail-ness

[ljwolf]

Our join count implementation for black-white tests only looks for negative spatial autocorrelation by default (i.e. if the observed black-white joins are substantially larger than simulated black-white joins). We should probably provide an option for two-tailed testing, since this seems to be a reasonable default assumption, that autocorrelation might be positive or negative.

[sjsrey]

+1.

It is actually an interesting testing problem as there are three component tests (WW, BW, BB) and one could think about joint versus marginal tests, as well as one and two-sided tests for each variant.

[ljwolf]

Yeah, I agree it's pretty interesting and open... I like thinking about the cross-color joins, but any might be useful. I think the right test for the bb/ww is on all same-color joins (BB +WW) rather than bb/ww alone.

And, thinking multivariate, the cross-color and same-color tests would be reasonable first steps, too.

Idk, just hit this when writing some teaching stuff, so figured I'd log it!

[ljwolf]

Hmm @rose-pearson, I can't assign this to you for some reason. Let's just tag your name here & that'll serve to let others know you've got this 😅

[rose-pearson]

Hi @ljwolf , I'm just working through this issue.

I have made the code changes that I believe are required to access the positive and negative autocorrelations.

I am now working through the quired additions to the tests. I was just wondering if there is a reason why the 'test_by_col' test in 'test_join_counts.py' only creates a limited subset of outcomes. i.e. is their a reason not to extend the outcomes to outvals = ['bb', 'bw', 'ww', 'p_sim_bw', 'p_sim_bb'] from outvals = ['bb','p_sim_bw', 'p_sim_bb']. Thanks!

[ljwolf]

I wouldn't extend that test. That test only checks that the statistic correctly processes columns of dataframes using the by_col method. It's not as important for that test to duplicate the effort done to ensure the actual statistic is correct. That occurs earlier in the test_join_counts.py file.

If the numerical results are correct for the test you write for the positive autocorrelation test, then the by_col method will just check that it by_col correctly applies the statistic across a dataframe.

[rose-pearson]

Great. That definitely makes sense. I just wanted to make sure that was the case. Thanks.

[ljwolf]

rad, thanks for checking!