# [Rd] zero-extent matrices (PR#958)

**Thomas Lumley
**
tlumley@u.washington.edu

*Wed, 30 May 2001 12:36:56 -0700 (PDT)*

On 30 May 2001, Peter Dalgaard BSA wrote:
>* tlumley@u.washington.edu writes:
*>*
*>* > In 1.2.3
*>* > matrix(nrow=10,ncol=0)%*%numeric(0)
*>* > returns a 10x1 matrix of 0s
*>* >
*>* > In todays 1.3 it returns a 10x1 matrix of miscellaneous junk.
*>* >
*>* > While both are probably wrong the latter is causing problems for survival.
*>*
*>* Acutally, I'd say that the 1.2.3 version is correct (sums over empty
*>* sets being zero is a standard convention).
*
I was thinking that a 10x0 matrix times a 0x0 matrix should be a 10x0
matrix
>*
*>* Hmm, 1.3.0 as of yesterday gives 10 zeros for me as does the one
*>* updated and compiled about 18:00 CET...
*
Initially it will give zero. The two operands contain pointers to the R
heap and the BLAS call is treating the objects pointed to as length 10 and
length 1 respectively and multiplying whatever happens to be there.
Initially this will be zeros.
-thomas
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