Good advice.
The issue was created.
http://code.google.com/p/sympy/issues/detail?id=3189
--
Alexey Gudchenko
On 24.03.2012 22:33, Alan Macdonald wrote:
> So it is a bug in Sympy. Doesn't seem very fixable. My matrix example
> shows that even simple calculations can go wrong if numbers are
> calculated symbolically. (I realize that my example is not GA, but the
> point still stands.) Thus it seems to me that you must provide, if at
> all possible, a way to tell your module to calculate numbers as floating
> points with a specified precision.
>
> On 12/03/24 1:11 PM, Alexey U. Gudchenko wrote:
>>
>> 24.03.2012 18:13, Alan Bromborsky пишет:
>>> If I run this -
>>>
>>> from sympy import *
>>>
>>>
>>> M = Matrix([ [1, .6, .6], [.6, 1, .9], [.6, .9, 1] ])
>>> print 'M =', M
>>> print 'eig values =',M.eigenvals()
>>> print 'eig vectors =',M.eigenvects()
>>>
>>> I get -
>>>
>>> M = [ 1, 0.6, 0.6]
>>> [0.6, 1, 0.9]
>>> [0.6, 0.9, 1]
>>> eig values = {0.489531364385073: 1, 2.41046863561493: 1,
>>> 0.100000000000000: 1}
>>> eig vectors =
>>> Traceback (most recent call last):
>>> File "EigenTest.py", line 8, in<module>
>>> print 'eig vectors =',M.eigenvects()
>>> File
>>> "/usr/local/lib/python2.7/dist-packages/sympy-0.7.1_git-py2.7.egg/sympy/matrices/matrices.py",
>>>
>>> line 2969, in eigenvects
>>> raise NotImplementedError("Can't evaluate eigenvector for
>>> eigenvalue
>>> %s" % r)
>>> NotImplementedError: Can't evaluate eigenvector for eigenvalue
>>> 0.489531364385073
>>>
>>> It runs right away (no delay) and gets the correct eigenvalues, but
>>> cannot calculate the eigenvectors. Any suggestions?
>>>
>>> The answer from Maple is -
>>>
>>> [2.410468637, 1, {vector([.5154991337, .6059127988, .6059128004])}],
>>> [.4895313645, 1, {vector([-.8568900997, .3645129341, .3645129324])}],
>>> [.999999991e-1, 1, {vector([.1078e-8, .7071067798, -.7071067815])}]
>>>
>>>
>>
>> It is related with this open issue:
>>
>> http://code.google.com/p/sympy/issues/detail?id=2193
>>
>> Alexey.
>>
>>
>
>
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