My data set has species with a number of morphological variables, including body mass:
species mass skull wing
a 10 4 4
b 15 3 5
c 30 2 6
d 40 5 9
But I want to look at a PCA of my data while controlling for body mass.
Is it appropriate to conduct regression models of skull ~ body mass
& wing ~ body mass
and use the residuals of these models in my PCA?