Updates:
Owner: someb...@bluewin.ch
Labels: Statistics
Comment #2 on issue 3104 by mrock...@gmail.com: Expectation value of random
variables raises maximum recursion depth exceeded
http://code.google.com/p/sympy/issues/detail?id=3104
This problem can be solved in a couple of ways.
One is what you point out - we can recognize and simplify complex
expressions into equivalent simple ones over different probability spaces.
The other is to improve the way we write down integrals. Right now I think
this computation introduces a DiracDelta(sqrt(X**2+Y**2+Z**2) - dummy) into
the integral and then asks deltaintegrate to take care of it.
deltaintegrate fails on this sort of thing. We can improve this either by
improving deltaintegrate or by no longer depending on it and writing our
own solution to this sort of thing. Nathan was talking about this earlier
and I had given it some though during the initial development.
Ideally both solutions would be in place. I suspect you're more interested
in the first while I'm more interested in the second.
Do you have an idea about how the first can be implemented in a general
way? Some sort of table lookup? Does anyone who knows more about SymPy have
wisdom on this topic?
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