Trying to compute the power of a matrix in R, I found that package expm implements the operator %^%.
So x %^% k computes the k-th power of a matrix.
> A<-matrix(c(1,3,0,2,8,4,1,1,1),nrow=3)
> A %^% 5
[,1] [,2] [,3]
[1,] 6469 18038 2929
[2,] 21837 60902 9889
[3,] 10440 29116 4729
but, to my surprise:
> A
[,1] [,2] [,3]
[1,] 691 1926 312
[2,] 2331 6502 1056
[3,] 1116 3108 505
somehow the initial matrix A has changed to A %^% 4 !!!
How do you perform the matrix power operation?
I have fixed that bug in the R-forge sources (of "expm" package), svn rev. 53. --> expm R-forge page For some reason the web page still shows rev.52, so the following may not yet solve your problem (but should within 24 hours):
install.packages("expm", repos="http://R-Forge.R-project.org")
Otherwise, get the svn version directly, and install yourself:
svn checkout svn://svn.r-forge.r-project.org/svnroot/expm
Thanks to "gd047" who alerted me to the problem by e-mail.
Note that R-forge also has its own bug tracking facilities.
Martint