[Numpy-discussion] Matrix Class [was numpy release]
Alan G Isaac
aisaac@american....
Tue Apr 29 00:04:27 CDT 2008
On Mon, 28 Apr 2008, Bill Spotz apparently wrote:
> If matrix multiplication in my example is replaced with
> np.dot() in yours, then when IS anything gained by using
> matrices?
When matrix algebra is clearer than array algebra.
But that is not the case for this algorithm.
(Just the opposite, I would say.)
Simple example: (X.T * X).I * (X.T * Y)
(Not that this is computationally nice ...)
> As for this example, my version should work with a properly
> implemented sparse_matrix A, but the array approach precludes that.
> That is to say, I could convert A to a matrix if it is provided as an
> array, but you could not convert a sparse_matrix to an array.
A.todense().A?
(I don't think you can save on memory use without
substantial changes...)
In an earlier discussion, I suggested that if iteration
over matrices were to yield 1d arrays, then iteration
over sparse matrices should yield 1d "sparse arrays".
Cheers,
Alan
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