I was wondering what is your recommended way to compute the inverse of a matrix?
The ways I found seem not satisfactory. For example,
> c=rbind(c(1, -1/4), c(-1/4, 1))
> c
[,1] [,2]
[1,] 1.00 -0.25
[2,] -0.25 1.00
> inv(c)
Error: could not find function "inv"
> solve(c)
[,1] [,2]
[1,] 1.0666667 0.2666667
[2,] 0.2666667 1.0666667
> solve(c)*c
[,1] [,2]
[1,] 1.06666667 -0.06666667
[2,] -0.06666667 1.06666667
> qr.solve(c)*c
[,1] [,2]
[1,] 1.06666667 -0.06666667
[2,] -0.06666667 1.06666667
Thanks!
Answer
solve(c) does give the correct inverse. The issue with your code is that you are using the wrong operator for matrix multiplication. You should use solve(c) %*% c to invoke matrix multiplication in R.
R performs element by element multiplication when you invoke solve(c) * c.