I'm using the R package vegan to perform canonical correspondence analysis (CCA). As input we have two matrices, one being (sites)x(species) and the other being (sites)x(conditions).
Sample data (and source of plot) are here.
Species loadings are easily accessed with
summary(cca_model)$species. What I'm trying to find is the loadings for the explanatory variables, the conditions. The only summary I can find is biplot scores. Looking through the documentation for
vegan I can't find any description of how they are computed. Can I sum them across CCA components to get an idea of how much they influence the data?
This is a biplot of two CCA components. The scores are used as coordinates for the arrows.
So two questions:
What are biplot scores in the context of CCA?
Can biplot scores be used to determine how much of an effect conditions have on the response variables?