[R] [ifelse] how to maintain a value from original matrix without probs?

[Henrik Bengtsson]

> A <- matrix(-4:4, ncol=3)
> A
     [,1] [,2] [,3]
[1,]   -4   -1    2
[2,]   -3    0    3
[3,]   -2    1    4
> Apos <- A; Apos[A <= 0] <- NA;
> Apos
     [,1] [,2] [,3]
[1,]   NA   NA    2
[2,]   NA   NA    3
[3,]   NA    1    4
> Aneg <- A; Aneg[A >= 0] <- NA
> Aneg
     [,1] [,2] [,3]
[1,]   -4   -1   NA
[2,]   -3   NA   NA
[3,]   -2   NA   NA

/Henrik

On Fri, Oct 31, 2008 at 7:59 AM, Diogo André Alagador
<mcnda839 at mncn.csic.es> wrote:
> Dear all,
>
> I have a matrix with positive and negative values.
> >From this I would like to produce 2 matrices:
> 1st - retaining positives and putting NA in other positions
> 2nd - retaining negatives and putting NA in other positions
>
> and then apply rowMeans for both.
>
> I am trying to use the function ifelse in the exemplified form:
> ifelse(A>0,A,NA)
> but by putting A as a 2nd parameter it changes dimensions of the original
> object.
>
> I wonder if I can do this, as it seems not to difficult.
>
> thanks in advance
>
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>
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