example PCA

# turn the data into a correlation matrix
cor(mydata)

# perform the PCA, using `principal`

pca.fit <- principal(mydata, 
            nfactors = ncol(mydata), # the number of factors = the number of columns in my data
            rotate = "varimax", # I want to perform varimax rotation on the factors
            residuals = TRUE, # report the residuals
            scores = TRUE)  # find the component scores