singular matrix

Chetan Jhurani chetan at
Thu Apr 16 15:05:15 CDT 2009

> From: Matthew Knepley
> On Thu, Apr 16, 2009 at 11:34 AM, Chetan Jhurani <chetan at> wrote:
> > Only a square matrix can be singular.
> No, a singular matrix has a kernel. A non-square matrix can be singular.  

One can generalize the concept of singular for rank-deficient rectangular
matrices, but almost all usual definitions of singular matrix use
non-invertibility or determinant and thus restrict themselves to
square matrices.

For example,

> > If rank(A) = n, see
> > <>
> QR will work for a matrix of rank < n. In this case, a null space basis fills out U.



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