You need brackets in i:(i+25) 3:3+25 is not want you 3:(3+25) is what you want. to explicitly print out values in a for loop you need to use print for (i in 1:10) { print(i) } Ole -- Ole F. Christensen Center for Bioinformatik Aarhus Universitet Ny Munkegade, Bygning 540 8000 Aarhus C