[R] matrix exponential: M^0

[John Fox]

Dear Federico,

The common arithmetic operators such as ^ operate on the elements of 
matrices (or vectors or arrays). Similarly, * gives the element-wise 
product and not the matrix product.

I hope that this helps,
  John

At 04:40 PM 1/20/2004 +0000, Federico Calboli wrote:
>Dear All,
>
>I would like to ask why the zeroeth power of a matrix gives me a matrix
>of ones rather than the identity matrix:
>
> > D<-rbind(c(0,0,0),c(0,0,0),c(0,0,0))
> > D<-as.matrix(D)
> > D
>      [,1] [,2] [,3]
>[1,]    0    0    0
>[2,]    0    0    0
>[3,]    0    0    0
>
> > D^0
>      [,1] [,2] [,3]
>[1,]    1    1    1
>[2,]    1    1    1
>[3,]    1    1    1
>
>I would have expected the identity matrix here.
>
>I find the same result with every other square matrix I used.
>BTW, I am using R 1.8.1 on Linux Mandrake 9.1
>
>Cheers,
>
>Federico Calboli

____________________________
John Fox
Department of Sociology
McMaster University
email: jfox at mcmaster.ca
web: http://www.socsci.mcmaster.ca/jfox