[R] Odp: what is there in a numeric (0)?

Petr PIKAL petr.pikal at precheza.cz
Thu Nov 27 13:35:42 CET 2008


r-help-bounces at r-project.org napsal dne 27.11.2008 11:48:32:

>  Hello!
>  I will repeat my question :what is there in a numeric(0)?
>  In a function, I have several matrices with dimensions 288x1, also 
> with dimensions 
>  0x1 (numeric(0)).
>  But I really do not know in which matrix there are elements or not.
>  So, these matrices that do not contain anything, if I am saying this 
> correctly, I would like to make them
>  matrices with the same dimensions as the first ones but with NA 
elements and 
> the ones with elements to remain as they 
>  are.
>  For this reason, I thought to use the ifelse command. But I have 
> determining the arguments of this ifelse...
>  I tried to use: 
>  A1 <- ifelse(nrow(A)==0,matrix(rep(NA,288),288,1),A)
>  If A is a matrix with elements, then I get a A1 matrix with replicated 
> times its first element, but I want the 
>  initial A matrix. If A is a matrix with no elements (numeric(0)) then I 
> only 1 NA. 

It is not a work for ifelse but for if. You want to test only one 
comparison not a vector of values.

if(nrow(mat)==0) A1 <- matrix(NA, 288,1) else A1 <- A


> So, how can I test if there are elements in my matrix and if there are 
> return itself the matrix and if there are not to get a matrix 288x1 with 
> Thank you for your time!
> Ismini
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