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rmatrixinverse

Different results for inverse of matrix

I have a 5 by 5 matrix:

t <- read.table(header=FALSE, 
text=" 1    0   0   -0.0000009038   0
0   1   0   0.0000000000    0
0   0   1   0.0000000000    0
0   0   0   1.0000000000    0
0   0   0   0.0000000000    1
")

When I try to take the inverse of this matrix, I get different results with

tt <- solve(t)

and

tt <- 1/(t)

Why? Shouldn't they both work?

Solution

  • 1/t is not the inverse of a matrix. It is rather elementwise reciprocal. Same way in math if you have a function, f(x), then 1/f(x) is not the inverse of the matrix.

    Note that even in math, the inverse of a matrix is never written as 1/A if A is a matrix.

    In R. The inverse of a matrix is computed as solve(A)