Comment #4 on issue 3129 by [email protected]: Drastic change to sympy.stats: Adding concept of Probability Distributions on surface level
http://code.google.com/p/sympy/issues/detail?id=3129

I certainly agree with the general idea.

I think that the main trouble with sympy.stats is that its objects don't map cleanly to established mathematical concepts. RandomSymbol does represent random variables, but PSpace and RandomDomain are odd beasts.

So, having a representation of probability distributions should simplify the design. The mathematical abstraction underlying them is the concept of measure (https://en.wikipedia.org/wiki/Measure_theory), and a Measure object mu would have one important method: mu.integrate(f, D) implementing \int_D f dµ. Implementing only the counting measure(https://en.wikipedia.org/wiki/Counting_measure) and the Lebesgue measure(https://en.wikipedia.org/wiki/Lebesgue_measure) would unify the discrete and continuous cases.

Note that for us, a measure and a measure space (or a probability distribution and a probability space) are the same thing, since a measure needs to "know" its domain of definition and thus has to contain all the information that makes up a measure space.

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