[Numpy-discussion] defmatrix.py

Charles R Harris charlesr.harris@gmail....
Mon Mar 26 17:30:49 CDT 2007


On 3/26/07, Travis Oliphant <oliphant@ee.byu.edu> wrote:
>
>
> > I think that might be the simplest thing, dot overrides subtypes. BTW,
> > here is another ambiguity
> >
> > In [6]: dot(array([[1]]),ones(2))
> >
> ---------------------------------------------------------------------------
> > exceptions.ValueError                                Traceback (most
> > recent call last)
> >
> > /home/charris/<ipython console>
> >
> > ValueError: matrices are not aligned
> >
> > Note that in this case dot acts like the rhs is always a column vector
> > although it returns a 1-d vector. I don't know that this is a bad
> > thing, but perhaps we should extend this behaviour to matrices, which
> > would be different from the now current 1-d is always a *row* vector,
> i.e.
>
>
> The rule 1-d is always a *row* vector only applies when converting to a
> matrix.
>
> In this case, the dot operator does not "convert to a matrix" but uses
> rules for operating with mixed 2-d and 1-d arrays inherited from Numeric.
>
> I'm very hesitant to change those rules.


I wasn't suggesting that, just noticing that the rule was 1-d vector on
right is treated as a column vector by dot, which is why an exception was
raised in the posted case. If it is traditional for matrix routines always
treat is as a row vector, so be it.

Chuck
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