non-monotonic correlation

[blancobercial]

Hello!

We are using gappa with metabarcoding of marine organisms and many of them they do not have a liner relationship with depth/density/temperature/etc., but they peak however an intermediate values (e.g., they will not be in 0-300, nor in 700-1000, but have the maxima only in the 500m range; both Pearson and Spearman will not find that significant). The available correlations assume a monotonic relationship, and I was wondering if it would be possible to add a non-monotonic correlation (Kendall, maybe?). Thank you for the software!

Best,

Leo