> Unfortunately, x^(-1) is not the inverse of x: > > x<-matrix(c(2,4,4,5),nrow=2) > x > # [,1] [,2] > # [1,] 2 4 > # [2,] 4 5 > > x^(-1) > # [,1] [,2] > # [1,] 0.50 0.25 > # [2,] 0.25 0.20 > > i.e. it is the matrix which you get by applying the operation > (...)^(-1) to each element of x. > > In R, the inverse of a non-singular matrix is (somewhat obscurely) > denoted by solve(x): > > solve(x) > # [,1] [,2] > # [1,] -0.8333333 0.6666667 > # [2,] 0.6666667 -0.3333333 > > solve(x)%*%x > # [,1] [,2] > # [1,] 1 1.110223e-16 > # [2,] 0 1.000000e+00 > (Note the slight rounding error); whereas > > (x^(-1))%*%x > # [,1] [,2] > # [1,] 2.0 3.25 > # [2,] 1.3 2.00
Thanks for the very detailed explanation! I will never make that mistake again =) ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
