On 2009-06-06 18:08, Carl Banks wrote:
On Jun 6, 3:31 pm, Robert Kern<robert.k...@gmail.com> wrote:
On 2009-06-06 17:09, John Machin wrote:
Robert Kern<robert.kern<at> gmail.com> writes:
You have a very singular matrix (2*a[1] - a[0] == a[2]). You cannot invert it
numerically and expect sensible results.
Is raising an exception (as documented
(http://docs.scipy.org/doc/numpy/reference/generated/numpy.linalg.inv....)) not
a "sensible result"?
That's not the way I was using the phrase, but you have a point.
We depend on the underlying LAPACK routine to tell us if the array is singular
or not.
Perhaps the documentation should be updated to say "Raises LinAlgError
if inv() detects that 'a' a singular matrix".
Anyone with much experience with linear algebra libraries should know
that these routines are shaky when ill-conditioned, but it could help
newbies and computer science experts to be explicit about it.
By all means, please do.
http://docs.scipy.org/numpy/Front%20Page/
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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