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. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
