R help - Oct 2010 - Plotting factors in biplots

Dear list, I'm trying to make a biplot, but instead of plotting the row
numbers for each observation, I'd like to plot a group factor.
Example:

  prcomp(iris[,1:4]) -> PCA
  biplot(PCA) #this makes a nice biplot but with row names

Instead of row numbers I want to plot iris[,5], which is a factor.
I can do this:

plot(PCA$x[,1], PCA$x[,2], type="n")
text(PCA$x[,1], PCA$x[,2], labels=iris[,5], col=palette()[iris[,5]])

Here I have a nice colored plot, but without the variable vectors.
Any tip?

Thanks a lot in advance.

A.

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