On 14-Feb-08 12:59:46, Martin Waller wrote:
> Hi,
> I guess this might be a FAQ or something, and there's
> probably a nice simple way to do it, but I can't think of it:
>
> Given a matrix, I want to remove columns that are _entirely_
> filled with NAs (partial NAs are fine).
>
> How please?
>
> Thanks,
> Martin
It probably isn't a FAQ (it's a somewhat special question)
but the following illustrates one way to do it:
M<-cbind(c(1,2,3,4),c(1,2,NA,4),c(NA,NA,NA,NA))
M
## [,1] [,2] [,3]
##[1,] 1 1 NA
##[2,] 2 2 NA
##[3,] 3 NA NA
##[4,] 4 4 NA
apply(M,2,function(x){!all(is.na(x))})
##[1] TRUE TRUE FALSE
M[,apply(M,2,function(x){!all(is.na(x))})]
## [,1] [,2]
##[1,] 1 1
##[2,] 2 2
##[3,] 3 NA
##[4,] 4 4
Ted.
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Date: 14-Feb-08 Time: 13:14:20
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