Greetings: In a function I'm trying to write I am multiplying each row in a matrix by a vector. When the vector extends beyond the end of the matrix I need to have the multiplication wrap around (continue with column 1 of the matrix). Initially I got this to work with a loop (old programming habits die hard). Now, after going back through MASS I've figured out how to do the multiplication efficiently (without loops) but I can't seem to solve the wrapping problem. Is there an efficient method for making vector multiplication wrap around the end of the matrix? I'm using R-2.0.0 running on Windows XP Pro 2002. Cheers, Kurt Wollenberg, PhD Tufts Center for Vision Research New England Medical Center 750 Washington St, Box 450 Boston, MA, USA kwollenberg at tufts-nemc.org 617-636-8945 (Fax) 617-636-9028 (Lab) The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" (I found it!) but "That's funny ..." --Isaac Asimov ********************** Confidentiality Notice\ **********************\ The inf...{{dropped}}