[R] Inverse Matrices

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Nov 6 16:27:40 CET 2001

On Tue, 6 Nov 2001 laura at bayesian-bay.freeserve.co.uk wrote:

> I have a problem with finding the inverse of a matrix. I have a square
> 9x9 matrix, A, and when I do solve(A) to find the inverse I get the
> following error message:
> Error in solve.default(A) : singular matrix `a' in solve
> Has anybody got any ideas as to why this is happening?

Because the matrix probably does not have an inverse, or is extremely
close to one that does not.  Look at its eigendecomposition or svd to
learn more.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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