R: color first 100 observations different than second 100 observations

Question

I have 200 observations with 6 features each, and I am trying to color the first 100 observations a different color than the second 100 observations. This is for principal component analysis. I have to insert some code with "col" inside my code but I do not know how to do this. Can anyone help? Thanks!

biplot(pr.out,scale=0,col=?)

Answer 1

The above comments are good advice, but the answer to your question is that you cannot use more than one color for the observations in the version of biplot in the stats package (see manual pages ?biplot.prcomp and ?biplot.default ). You can use different symbols however:

PCA <- prcomp(USArrests, scale = TRUE)
sym <- c(rep("x", 25), rep("o", 25))
biplot(PCA, scale=0, xlabs=sym)