[R] Question about NULL matrix? Can I define a NULL matrix in R?

[David Winsemius]

On Aug 10, 2011, at 9:22 PM, Rolf Turner wrote:

> On 11/08/11 13:11, David Winsemius wrote:
>>
>> 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.
>>
>
> Wrong-oh, David.  :-) Check this out:

0 is an integer.

Cheers back.

>
> > m <- matrix(0,nrow=0,ncol=5)
> > m
>    [,1] [,2] [,3] [,4] [,5]
>
>    cheers,
>
>        Rolf
>

David Winsemius, MD
West Hartford, CT