R help - May 2011 - removing columns

Hi list,

I have a matrix with all elements of some columns are zeroes.  Is it
possible to remove these columns
and create a new matrix
nuncio




-- 
Nuncio.M
Research Scientist
National Center for Antarctic and Ocean research
Head land Sada
Vasco da Gamma
Goa-403804

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On 03.05.2011 13:16, nuncio m wrote:
> Hi list,
>
> I have a matrix with all elements of some columns are zeroes.  Is it
> possible to remove these columns:

Xnew <- X[ , as.logical(colSums(X)), drop=FALSE]

Uwe Ligges

> and create a new matrix
> nuncio
>
>
>
>

On May 3, 2011, at 4:24 AM, Uwe Ligges wrote:
>
>
> On 03.05.2011 13:16, nuncio m wrote:
>> Hi list,
>>
>> I have a matrix with all elements of some columns are zeroes.  Is it
>> possible to remove these columns:
>
>
> Xnew <- X[ , as.logical(colSums(X)), drop=FALSE]
A counter-example:

X <- matrix(c(1,1,1,-1,0,1,1,1,1),3)

A fix:
 > Xnew <- X[ , as.logical(colSums(abs(X))), drop=FALSE]
 > Xnew
      [,1] [,2] [,3]
[1,]    1   -1    1
[2,]    1    0    1
[3,]    1    1    1
>
> Uwe Ligges
>
>
>> and create a new matrix
>> nuncio

David Winsemius, MD
Heritage Laboratories
West Hartford, CT