Status: Valid
Owner: ----
Labels: Type-Enhancement Priority-Low Statistics
New issue 3555 by [email protected]: Simplify Stats expressions
http://code.google.com/p/sympy/issues/detail?id=3555
SymPy.stats doesn't attempt to simplify expressions given statistical
knowledge. Instead it generates integrals and trusts in those more mature
algorithms.
This fails in a number of solvable cases. A simple example
X = Normal('X', mu, sigma)
expr = X**2
density(expr)
This fails (the integral is difficult to solve/simplify) but the density of
X**2 is well known as a special case of the chi-squared distribution.
By adding another simplification layer at the higher statistical level we
can likely simplify many more problems.
I was motivated to post this because I stumbled across this visual database
of relations between distributions
http://www.math.wm.edu/~leemis/chart/UDR/UDR.html
These would be relatively simple to implement with unification and rewrite
rules if anyone wants to give it a try.
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