R help - Feb 2010 - rownames cannot allocate vector of size

Hi,

On R 2.10.1 for Windows, when I do the following to duplicate the 
structure of a large numeric matrix called matrix1:

matrix2 <- matrix(0,nrow=nrow(matrix1),ncol=ncol(matrix1))

and then

rownames(matrix2) <- rownames(matrix1)

I get a "cannot allocate vector of size xxMb" error

but if I instead do:

rnames <- list()
rnames <- rownames(matrix1)
matrix2 <- matrix(0,nrow=nrow(matrix1),ncol=ncol(matrix1),dimnames=rnames)

I get no error.

Of course both approaches work in R on Unix without memory limits.  But 
I'm intrigued about the apaprent difference in memory usage/allocation 
for the two above approaches. Is there any explanation for this 
difference in behaviour?

thanks
Tony

assigning rownames (after the object is created) triggers a copy of
the object... if you assign the rownames at creation time, no extra
copies...

b

On Mon, Feb 22, 2010 at 9:46 AM, Larson, TR <trl1 at york.ac.uk>
wrote:
> Hi,
>
> On R 2.10.1 for Windows, when I do the following to duplicate the structure
> of a large numeric matrix called matrix1:
>
> matrix2 <- matrix(0,nrow=nrow(matrix1),ncol=ncol(matrix1))
>
> and then
>
> rownames(matrix2) <- rownames(matrix1)
>
> I get a "cannot allocate vector of size xxMb" error
>
> but if I instead do:
>
> rnames <- list()
> rnames <- rownames(matrix1)
> matrix2 <-
matrix(0,nrow=nrow(matrix1),ncol=ncol(matrix1),dimnames=rnames)
>
> I get no error.
>
> Of course both approaches work in R on Unix without memory limits. ?But
I'm
> intrigued about the apaprent difference in memory usage/allocation for the
> two above approaches. Is there any explanation for this difference in
> behaviour?
>
> thanks
> Tony
>
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