Hi Henrik! On Fri, Oct 17, 2008 at 5:37 PM, henjo <[EMAIL PROTECTED]> wrote: > > Hi, > > I have been using Sympy for quite some time now in a symbolic electric > circuit solver (which I will release soon). > > To the problem, I have a matrix that gives an incorrect inverse: > >>>> A = Matrix([[x+y, -x, 0], [-x-y, x, 1], [0,1,0]]) >>>> Ainv = A.inv() >>>> Ainv.simplify() >>>> print Ainv > ⎡0 0 0⎤ > ⎢ ⎥ > ⎢0 0 1⎥ > ⎢ ⎥ > ⎣0 1 0⎦ >>>> print A*Ainv > ⎡ 0 0 0⎤ > ⎢ ⎥ > ⎢ 0 1 0⎥ > ⎢ ⎥ > ⎣-x - y x 1⎦
Thanks for the bug report. I made it: http://code.google.com/p/sympy/issues/detail?id=1168 In the meantime, use a different method for calculating the inverse, e.g.: In [1]: A = Matrix([[x+y, -x, 0], [-x-y, x, 1], [0,1,0]]) In [2]: Ainv = A.inv("ADJ") In [3]: Ainv Out[3]: ⎡ -1 -x ⎤ ⎢────── 0 ──────⎥ ⎢-x - y -x - y⎥ ⎢ ⎥ ⎢ 0 0 1 ⎥ ⎢ ⎥ ⎣ 1 1 0 ⎦ In [4]: Ainv*A Out[4]: ⎡ x y ⎤ ⎢- ────── - ────── 0 0⎥ ⎢ -x - y -x - y ⎥ ⎢ ⎥ ⎢ 0 1 0⎥ ⎢ ⎥ ⎣ 0 0 1⎦ In [6]: (Ainv*A).applyfunc(simplify) Out[6]: ⎡1 0 0⎤ ⎢ ⎥ ⎢0 1 0⎥ ⎢ ⎥ ⎣0 0 1⎦ If you have time, it'd be cool if you could figure out where the problem is exactly, see the issue. Looking forward for your symbolic electric circuit solver. When you release it, please send also an email to this list, I am sure people will like to play with it. Well, to speak for myself, I will. :) Ondrej --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sympy?hl=en -~----------~----~----~----~------~----~------~--~---
