On Thu, Jun 5, 2008 at 4:32 PM, Robert Cimrman <[EMAIL PROTECTED]> wrote:
>
> Ondrej Certik wrote:
>> I just discovered we probably need to think about this:
>>
>> In [1]: a = Matrix((1, x), (2, y))
>>
>> In [2]: from numpy import array
>>
>> In [3]: a
>> Out[3]:
>> ⎡1 x⎤
>> ⎣2 y⎦
>>
>> In [4]: Matrix(sin(array(a)))
>> Out[4]:
>> ⎡sin(1) sin(x)⎤
>> ⎣sin(2) sin(y)⎦
>>
>> In [5]: sin(a)
>> [...]
>>
>> AttributeError: 'Matrix' object has no attribute 'is_Number'
>>
>>
>> What should [5] return? The same as [4] or the sin of a Matrix, which
>> is defined as sin(A) = Q*sin(D)*Q^T if A = Q*D*Q^T and D is
>> diagonal, so sin(D) is just the D with sin applied to the diagonal
>> terms.
>
> This stuff generates neverending discussions on numpy lists. Numpy
> currently solves this by having array (n-dimensional container) and
> matrix (special 2d array w.r.t. multiplication and some functions). As
Well, not for sin:
In [8]: from numpy import matrix, array, sin
In [11]: a = matrix([[1,2],[3,0]])
In [12]: sin(a)
Out[12]:
matrix([[ 0.84147098, 0.90929743],
[ 0.14112001, 0. ]])
In [13]: sin(array(a))
Out[13]:
array([[ 0.84147098, 0.90929743],
[ 0.14112001, 0. ]])
So that's not how I would like this to be. It should either work for
all functions or for no functions.
> Matrix in SymPy is a linear algebra matrix, it should IMHO behave as
> such, i.e. sin(A) = Q*sin(D)*Q^T. Then maybe an Array would be usefull,
> something like sympy version of list of lists [of lists...].
Yes, I think so too. Plus we could create some pure python arrray
implementation, fully compatible with numpy.
Ondrej
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