[Octave-bug-tracker] [bug #46103] inversion of a singular diagonal matrix A produces inv(A)==A

[Mike Miller]

Follow-up Comment #1, bug #46103 (project octave):

Thanks for your bug report. This does not appear to be documented, but when
inverting a singular diagonal matrix, the original matrix is returned.

As you've noticed, and as the documentation for inv() clearly states, there
are often better ways to solve the problem using mldivide, or pinv.

Also, if you like this answer better,


octave:1> inv(diag(0:2))
warning: matrix singular to machine precision, rcond = 1
ans =

Diagonal Matrix

   0   0   0
   0   1   0
   0   0   2

octave:2> inv(full(diag(0:2)))
warning: matrix singular to machine precision
ans =

   Inf   Inf   Inf
   Inf   Inf   Inf
   Inf   Inf   Inf



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