search for: ccollin

...or each species. My programming skills are still somewhat rudimentary (and biased toward VBA-style looping...which seems to be leading me astray). Though I have searched, I have not yet seen this particular problem addressed in the help files. Many thanks for any suggestions, Cathy <mailto:ccollins at ku.edu>

Many thanks for your responses. I realize I made the first-time-poster's error of not giving an example of the data. There actually are no NA values, so I'm not simply replacing values in the data frame. So, the number of species (and therefore abundance values) listed in each treatment differs, even though they all have the same number of plots sampled. Sample_ID Spec_num Species_ID