[Numpy-discussion] matrix wart
Travis E. Oliphant
oliphant@enthought....
Fri Feb 22 08:55:41 CST 2008
Konrad Hinsen wrote:
> On 22.02.2008, at 01:10, Alan G Isaac wrote:
>
>
>> Someone once pointed out on this list that one might
>> consider a matrix to be a container of 1d vectors. For NumPy,
>> however, it is natural that it be a container of 1d arrays.
>> (See the discussion for the distinction.)
>>
>
> If I were to design a Pythonic implementation of the mathematical
> concept of a matrix, I'd implement three classes: Matrix,
> ColumnVector, and RowVector. It would work like this:
>
> m = Matrix([[1, 2], [3, 4]])
>
> m[0, :] --> ColumnVector([1, 3])
> m[:, 0] --> RowVector([1, 2])
>
These seem backward to me. I would think that m[0,:] would be the
RowVector([1,2]) and m[:,0] be the ColumnVector([1,3]).
> m[0,0] --> 1 # scalar
>
> m.shape --> (2, 2)
> m[0].shape --> (2,)
>
What is m[0] in this case? The same as m[0, :]?
> However, the matrix implementation in Numeric was inspired by Matlab,
> where everything is a matrix. But as I said before, Python is not
> Matlab.
It should be kept in mind, however, that Matlab's matrix object is used
successfully by a lot of people and should not be dismissed as irrelevant.
I would like to see an improved Matrix object as a built-in type (for
1.1). I am aware of two implementations that could be referred to in
creating it: CVXOPT's matrix object and NumPy's matrix object. There
may be others as well.
If somebody has strong feelings about this sufficient to write a matrix
built-in, then the door is wide open.
Best,
-Travis
More information about the Numpy-discussion
mailing list