R help - Aug 2011 - Question about NULL matrix? Can I define a NULL matrix in R?

Hi All, 
I would like to create a matrix in R but I dont know the size of my matrix. I
only know the size of the columns but not the size of the rows. So, is there any
way to create a dynamic matrix of size NULL by n_cols? and then add to that
matrix?
I know for a vector, I can do this: x= NULL but is there any way to do the same
for a matrix as well?
Thanks a lot,Andra
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On Aug 10, 2011, at 8:23 PM, Andra Isan wrote:
> Hi All,
> I would like to create a matrix in R but I dont know the size of my  
> matrix. I only know the size of the columns but not the size of the  
> rows. So, is there any way to create a dynamic matrix of size NULL  
> by n_cols? and then add to that matrix?
> I know for a vector, I can do this: x= NULL but is there any way to  
> do the same for a matrix as well?
No. You cannot make an R matrix without knowing the number of rows. By  
definition an R matix has two integer dimensions. Alternatives: You  
can rbind to an existing matrix, or you can make a larger than  
necessary matrix filled with NA's and then fill and later extract a  
subset of the rows.

-- 
David Winsemius, MD
West Hartford, CT