R help - Nov 2009 - reduce matrix

I am trying to reduce the dimension of matrix by removing zero elements and
creating a sub-matrix.

For example:

A= [1,0,0,3;  0,1,2,0; 0,0,3,5]

then the new matrix B would be:

B= [1,3;1,2;3,5]

There are the same number of zero elements in each row of A so dimension of B
will not be a problem. Is there a straightforward way to do this in R without
writing a function using loops etc?

Any help or suggestions would be appreciated!

Thanks

one way is the following:

A <- rbind(c(1,0,0,3), c(0,1,2,0), c(0,0,3,5))
t(apply(A, 1, function (x) x[x != 0]))


I hope it helps.

Best,
Dimitris


lloyd barcza wrote:
> I am trying to reduce the dimension of matrix by removing zero elements and
creating a sub-matrix.
> 
> For example:
> 
> A= [1,0,0,3;  0,1,2,0; 0,0,3,5]
> 
> then the new matrix B would be:
> 
> B= [1,3;1,2;3,5]
> 
> There are the same number of zero elements in each row of A so dimension of
B will not be a problem. Is there a straightforward way to do this in R without
writing a function using loops etc?
> 
> Any help or suggestions would be appreciated!
> 
> Thanks
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014

On Wed, 18 Nov 2009 04:18:08 -0800 (PST) lloyd barcza 
<floydeon at yahoo.com> wrote:
> I am trying to reduce the dimension of matrix by removing 
> zero elements and creating a sub-matrix.
> 
> For example:
> 
> A= [1,0,0,3;  0,1,2,0; 0,0,3,5]
> 
> then the new matrix B would be:
> 
> B= [1,3;1,2;3,5]
> 
> There are the same number of zero elements in each row of A 
> so dimension of B will not be a problem.
This should work:

B=matrix(t(A)[t(A)!=0], nrow=nrow(A), byrow=TRUE)

-- 
Karl Ove Hufthammer