[R] remove columns containing all zeros (or other value)

[andrew]

or this

x[,!(colSums(abs(x)) == 0)]

On Jan 15, 10:00 am, Marc Schwartz <wdwgol... at gmail.com> wrote:
> Careful:
>
> x <- matrix(c(1, 5, 3, 2, 1, 4, -1, 0, 1),
>             ncol = 3, nrow = 3)
>
> > x
>
>      [,1] [,2] [,3]
> [1,]    1    2   -1
> [2,]    5    1    0
> [3,]    3    4    1
>
> > x[, colSums(x) != 0]
>
>      [,1] [,2]
> [1,]    1    2
> [2,]    5    1
> [3,]    3    4
>
> Not quite the result wanted...  :-)
>
> Try this:
>
> > x[, colSums(x == 0) != nrow(x)]
>
>      [,1] [,2]
> [1,]    1    2
> [2,]    5    1
> [3,]    3    4
>
> x <- matrix(c(1, 5, 3, 2, 1, 4, -1, 0, 1),
>               ncol = 3, nrow = 3)
>
> > x[, colSums(x == 0) != nrow(x)]
>
>      [,1] [,2] [,3]
> [1,]    1    2   -1
> [2,]    5    1    0
> [3,]    3    4    1
>
> HTH,
>
> Marc Schwartz
>
> on 01/14/2009 04:29 PM Gustavo Carvalho wrote:
>
>
>
> > Sorry for the double post, but this is probably faster:
>
> > x[, colSums(x) != 0]
>
> > On Wed, Jan 14, 2009 at 8:22 PM, Gustavo Carvalho
> > <gustavo.bi... at gmail.com> wrote:
> >> You can also try this:
>
> >> x[,-(which(colSums(x) == 0))]
>
> >> Cheers,
>
> >> Gustavo.
>
> >> On Wed, Jan 14, 2009 at 8:01 PM, Anthony Dick <ad... at uchicago.edu> wrote:
> >>> Hello-
>
> >>> I would like to remove the columns of a matrix that contain all zeros. For
> >>> example, from
> >>> x<-matrix(c(1,5,3,2,1,4,0,0,0), ncol=3,nrow=3)
>
> >>> I would like to remove the third column. However, because this is in a loop
> >>> I need a way to first determine which columns are all zeros, and only then
> >>> remove them. I.e., I don't know which column of x contains all zeros until
> >>> after x is created.
>
> >>> Thanks!
>
> >>> Anthony
>
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