Under platform i686-pc-linux-gnu arch i686 os linux-gnu system i686, linux-gnu status major 1 minor 6.1 year 2002 month 11 day 01 language R and using acepack 1.3-2, ace() and avas() have checks such as if(circ[i] < 0 || circ[i] > nrow(x)) { if(mon[i] < 0 || mon[i] > nrow(x)) { if(lin[i] < 0 || lin[i] > nrow(x)) { etc. I believe that nrow should be ncol. Also, in ace() there is the follwing check: if (cat[i] == 0) { cat("response spec can only be lin or ordered (default)") return() } whereas I believe that the ace algorithm does allow for categorical response variables. -- Frank E Harrell Jr Prof. of Biostatistics & Statistics Div. of Biostatistics & Epidem. Dept. of Health Evaluation Sciences U. Virginia School of Medicine http://hesweb1.med.virginia.edu/biostat