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

jass at in.gr jass at in.gr
Thu Nov 27 11:48:32 CET 2008

 I will repeat my question :what is there in a numeric(0)?

 In a function, I have several matrices with dimensions 288x1, also matrices 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 
 For this reason, I thought to use the ifelse command. But I have problems 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 288 times its first element, but I want the  
 initial A matrix. If A is a matrix with no elements (numeric(0)) then I get only 1 NA.  
So, how can I test if there are elements in my matrix and if there are to return itself the matrix and if there are not to get a matrix 288x1 with NAs?
Thank you for your time!


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