on 09/03/2008 10:34 AM Chuck Cleland wrote: > On 9/3/2008 11:05 AM, Petr PIKAL wrote: >> [EMAIL PROTECTED] napsal dne 03.09.2008 15:54:08: >> >>> try this: >>> >>> x <- c(3,3,3,3,0,0,0,0,5,5,5,5,8,8,8,8) >>> x <- matrix(x, nrow=4) >>> >>> which(colSums(x == 0) == nrow(x)) >> Isn't this the same? >> >> which(colSums(x)==0) > > No, because the column sum can be zero without each element being zero: > > x <- c(3,3,3,3,1,-1,1,-1,5,5,5,5,8,8,8,8) > x <- matrix(x, nrow=4) > >> which(colSums(x == 0) == nrow(x)) > integer(0) > >> which(colSums(x)==0) > [1] 2 >
Another (column-wise) approach to this would be: x <- c(3,3,3,3,0,0,0,0,5,5,5,5,8,8,8,8) x <- matrix(x, nrow=4) > which(apply(x, 2, function(i) all(i == 0))) [1] 2 x <- c(3,3,3,3,1,-1,1,-1,5,5,5,5,8,8,8,8) x <- matrix(x, nrow=4) > which(apply(x, 2, function(i) all(i == 0))) integer(0) HTH, Marc Schwartz ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
