I need to check the effects of three explanatory variables which are 1) fish_length, location, and sex on a set of response variables (PC1…..PC7).
First I need to test the effect of size (fish size), and in case if the effect of fish_length is significant then I need to use the residuals of the first pRDA test to check the effects of location and sex using RDA. Also I will need to use the residuals of the first pRDA test in “discriminant analysis”.
How can I get the “residuals of the pRDA” analysis? Please check the attachment. I try rda() in vegan package, but couldn't get the results.