This function subjects the trait variables from the original dataset to the
Principal component analysis (PCA, stats:prcomp) and calculates
principal componenets scores for each sample. All variables are centered by
subtracting the variable mean from a particular value and scaled to the unit
variance by dividing the value by the standard deviation of a trait
(stats::prcomp parameters center = T, scale = T). Some
functions like, for example, calcHS require uncorrelated input
variables to calculate individual identity information properly.