Hi, This should do what you are looking for: x <- matrix(1:10, byrow = TRUE, nrow = 2) mapply(function(x1, x2) x1+x2, x[1, ], x[2, ]) But have also a look at colSums and colMeans HTH Thomas -----Urspr?ngliche Nachricht----- Von: Fredrik Lundgren [mailto:fredrik.lundgren at norrkoping.mail.telia.com] Gesendet: Dienstag, 23. Dezember 2003 10:00 An: R-help Betreff: [R] unary operations Hello, I had expected that the following should work mat <- matrix(c(5, 7, 6, 7, 8, 10, 17, 28, 36, 41, 46, 140), nrow = 2, byrow = T) mat apply(mat, 2, function(e1,e2) e1*e2) apply(mat, 2, function(e1,e2) e1+e2) apply(mat, 2, function(e1,e2) e1-e2) apply(mat, 2, function(e1,e2) e1/e2) but I get Error in FUN(newX[, i], ...) : Argument "e2" is missing, with no default What do I do wrong? Sincerely Fredrik Lundgren ______________________________________________ R-help at stat.math.ethz.ch mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help