R help - Nov 2007 - when deleting a row from a matrix gives a vector

Deleting a row from a matrix turns it into a vector (and dim names  
are lost) if the resulting matrix has only one row or column. For  
instance:

 > x <- matrix(1:10, ncol=2)
 > x <- x[1,]

turns x into

[1] 1 6

instead of

      [,1] [,2]
[1,]    1    6

Is there any way to force the result to remain a matrix, even if it  
has only one row or column, or even only one entry? Thanks,

Gabriel

x <- x[1, drop=FALSE]
> Is there any way to force the result to remain a matrix, even if it
> has only one row or column, or even only one entry? Thanks,
-- 
Sarah Goslee
http://www.functionaldiversity.org

On Fri, 2007-11-02 at 20:47 +0100, Gabriel Valiente
wrote:
> Deleting a row from a matrix turns it into a vector (and dim names  
> are lost) if the resulting matrix has only one row or column. For  
> instance:
> 
>  > x <- matrix(1:10, ncol=2)
>  > x <- x[1,]
> 
> turns x into
> 
> [1] 1 6
> 
> instead of
> 
>       [,1] [,2]
> [1,]    1    6
> 
> Is there any way to force the result to remain a matrix, even if it  
> has only one row or column, or even only one entry? Thanks,
> 
> Gabriel
See R FAQ 7.5 Why do my matrices lose dimensions?

http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-do-my-matrices-lose-dimensions_003f

HTH,

Marc Schwartz

On Nov 2, 2007, at 12:50 PM, Sarah Goslee wrote:
> x <- x[1, drop=FALSE]
>
>> Is there any way to force the result to remain a matrix, even if it
>> has only one row or column, or even only one entry? Thanks,
I think you might have meant ...

x <- x[1,,drop=FALSE]

Note the double commas ...

- VV
===
> -- 
> Sarah Goslee
> http://www.functionaldiversity.org

On Fri, 2 Nov 2007, Gabriel Valiente wrote:
> Is there any way to force the result to remain a matrix, even if it
> has only one row or column, or even only one entry? Thanks,
>

Yes. See the FAQ entry or the help page.

       -thomas


Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle