Re: [Numpy-discussion] Matrix Class

[cjw]

Thanks Sebastian, This would appear to make a case for considering not having Matrix as a sub-class of an np array. On the other hand, so much work has gone into np, and there is some commonality between the needs of Matrix and Array. Colin W. On 11-Feb-15 12:19 PM, Sebastian Berg wrote: On Mi, 2015-02-11 at 11:38 -0500, cjw wrote: 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? No, I just mean the fact that a matrix is always 2D. This makes some things like some indexing operations awkward and some functions that expect a numpy array (but think they can handle subclasses fine) may just plain brake. And then ndarray subclasses are just a bit problematic.... In short, you cannot generally expect a function which works great with arrays to also work great with matrices, I believe. this is true for some things within numpy and certainly for third party libraries I am sure. - Sebastian 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]] -- View this message in context: http://numpy-discussion.10968.n7.nabble.com/Matrix-Class-tp39719.html Sent from the Numpy-discussion mailing list archive at Nabble.com. _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion

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