Hi, I'd like to plot the results of PCA in biplots, grouping the observations by using different symbols. With xyplot in lattice I can easily differentiate the groups (see for example DAAG, p 285) but it seems difficult (or impossible?) to plot the vectors for the variables as well as xyplot cannot handle secondary axis very well. Using the basic plot I can combine observations and variables in one plot but cannot differentiate the groups of observations as easily as in xyplot. What could I do to get grouped observations in a biplot? Thanks already, Kim __________________________________________ Kim Milferstedt University of Illinois at Urbana-Champaign Department of Civil and Environmental Engineering 4125 Newmark Civil Engineering Building 205 North Mathews Avenue MC 250 Urbana, IL 61801 USA phone: (001) 217 333-9663 fax: (001) 217 333-6968 email: milferst at uiuc.edu http://cee.uiuc.edu/research/morgenroth