On Thu, Jan 8, 2009 at 5:52 AM, Christian Kamenik <
christian.kame...@giub.unibe.ch> wrote:
>
> 'Apply' is a great thing for running functions on rows or columns of a
> matrix:
>
> X <- rnorm(20, mean = 0, sd = 1)
> dim(X) <- c(5,4)
> apply(X,2,sum)
>
> Is there a way to use apply for excluding rows or columns from a matrix to
> run functions on the remaining rows or columns?
X <- matrix(1:30,5,6)
> X
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 6 11 16 21 26
[2,] 2 7 12 17 22 27
[3,] 3 8 13 18 23 28
[4,] 4 9 14 19 24 29
[5,] 5 10 15 20 25 30
> X[c(-1,-3,-5),c(-2,-4)]
[,1] [,2] [,3] [,4]
[1,] 2 12 22 27
[2,] 4 14 24 29
> apply(X[c(-1,-3,-5),c(-2,-4)],c(1),sum)
[1] 63 71
> apply(X[c(-1,-3,-5),c(-2,-4)],c(2),sum)
[1] 6 26 46 56
> apply(X[c(-1,-3,-5),2:4],1,sum)
[1] 36 42
> apply(X[c(-1,-3,-5),c(1,3,5,6)],2,sum)
[1] 6 26 46 56
> apply(X[c(-1,-3,-5),c(T,F,T,F,T,T)],2,sum)
[1] 6 26 46 56
[[alternative HTML version deleted]]
______________________________________________
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.
