One problem with the matrix class is that it follows matlab way too much. For example:
>>> a = arange(9).reshape(3,3) >>> A = asmatrix(a) >>> v = arange(3) >>> dot(a, v) array([ 5, 14, 23]) >>> A*v Traceback (most recent call last): File "<pyshell#15>", line 1, in <module> A*v File "C:\Python25\lib\site-packages\numpy\core\defmatrix.py", line 157, in __mul__ return N.dot(self, asmatrix(other)) ValueError: objects are not aligned I do a lot of colour image processing. Most of the time I treat an image as a MxNx3 array, but some time I have to do matrix/ vector operations like colour-space conversion. In these cases the dot function becomes very handy (better then Matlab matrix multiplication), since I can write: new_image = dot(old_image, A) where A is either a 3x3 matrix or a length 3 vector. The result is that my code is cluttered with a lot of "dot"s, and the matrix class can not help much. It is possible that my case is special and does not justify a special attention, but if many of us do colour/spectral imaging, or other type of high-rank tensors algebra, there could be a case to give numpy an edge. Nadav. -----הודעה מקורית----- מאת: [EMAIL PROTECTED] בשם Travis E. Oliphant נשלח: ש 22-מרץ-08 01:12 אל: Discussion of Numerical Python נושא: Re: [Numpy-discussion] matrices in 1.1 Charles R Harris wrote: > > > On Fri, Mar 21, 2008 at 1:57 PM, Alan G Isaac <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > On Fri, 21 Mar 2008, Nadav Horesh apparently wrote: > > But asmatrix returns a matrix object and any subsequent > > operation of it returns a matrix. What I am thinking about > > is a convenient way to apply matrix operation on an array. > > I suspect what you are really wanting is a way for NumPy to > define new operators ... > > > I still kinda like the idea of using the call operator for matrix > multiplication, i.e. A(v) := dot(A,v). Interesting idea. I kind of like that too. -Travis _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
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