Re: [Numpy-discussion] Matrix Class

cjw Wed, 11 Feb 2015 08:40:04 -0800

On 11-Feb-15 10:47 AM, Sebastian Berg wrote:

On Di, 2015-02-10 at 15:07 -0700, cjw wrote:

It seems to be agreed that there are weaknesses in the existing Numpy Matrix
Class.


Some problems are illustrated below.

Not to delve deeply into a discussion, but unfortunately, there seem far
more fundamental problems because of the always 2-D thing and the simple
fact that matrix is more of a second class citizen in numpy (or in other
words a lot of this is just the general fact that it is an ndarray
subclass).

Thanks Sebastian,

We'll have to see what comes out of the discussion.

I would be grateful if you could expand on the "always 2D thing". Is there a need for a collection of matrices, where a function is applied to each component of the collection?

Colin W.


I think some of these issues were summarized in the discussion about the
@ operator. I am not saying that a matrix class separate from numpy
cannot solve these, but within numpy it seems hard.

I'll try to put some suggestions over the coming weeks and would appreciate
comments.

Colin W.

Test Script:

if __name__ == '__main__':
    a= mat([4, 5, 6])                   # Good
    print('a: ', a)
    b= mat([4, '5', 6])                 # Not the expected result
    print('b: ', b)
    c= mat([[4, 5, 6], [7, 8]])         # Wrongly accepted as rectangular
    print('c: ', c)
    d= mat([[1, 2, 3]])
    try:
        d[0, 1]= 'b'                    # Correctly flagged, not numeric
    except ValueError:
        print("d[0, 1]= 'b'             # Correctly flagged, not numeric", '
ValueError')
    print('d: ', d)

Result:

*** Python 2.7.9 (default, Dec 10 2014, 12:28:03) [MSC v.1500 64 bit
(AMD64)] on win32. ***

a:  [[4 5 6]]
b:  [['4' '5' '6']]
c:  [[[4, 5, 6] [7, 8]]]
d[0, 1]= 'b'             # Correctly flagged, not numeric  ValueError
d:  [[1 2 3]]





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Re: [Numpy-discussion] Matrix Class

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