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

[Erik Iverson]

Hello -

Diogo André Alagador 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 cannot reproduce this:

a <- matrix(sample(-10:10, 100, replace = TRUE), nrow = 10)
ifelse(a > 0 , a, NA)

gives me a 10 x 10 matrix of positive values and NA values, with 10 x 10 
being the original dimensions of a.


rowMeans(ifelse(a > 0 , a, NA), na.rm = TRUE)

gives me what you'd like for positive values, I think?



>  
> I wonder if I can do this, as it seems not to difficult.
>  
> thanks in advance
> 
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