request: How to get column name
on 09/03/2008 10:34 AM Chuck Cleland wrote:
On 9/3/2008 11:05 AM, Petr PIKAL wrote:
r-help-bounces at r-project.org 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