Comment #1 on issue 3711 by [email protected]: probability() should
handle union and intersection of conditions as well as point conditions
http://code.google.com/p/sympy/issues/detail?id=3711
You are using the wrong syntax to represent the (in)equalities:
1) `X = 2` used in the call to a function means a keyword argument, not an
equality.
2) python's `or` and `and` are short circuit operators, not suitable for
symbolic.
You need to use the symbolic `Eq`, `Or`, and `And` instead. Nevertheless,
when I do that, there is still a bug with calculating the probability for
the normal distribution:
from sympy import And, Or, Eq
from sympy.stats import Die, P, Normal
X = Die('X', 6)
Y = Normal('Y', 0, 1)
P(Eq(X, 2))
1/6
P(Eq(Y, 0))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "sympy/stats/rv.py", line 573, in probability
return pspace(condition).probability(condition, **kwargs)
File "sympy/stats/crv.py", line 305, in probability
return integrate(pdf(z), (z, domain.set), **kwargs)
File "sympy/utilities/decorator.py", line 25, in threaded_func
return func(expr, *args, **kwargs)
File "sympy/integrals/integrals.py", line 1481, in integrate
return integral.doit(deep=False, meijerg=meijerg, conds=conds,
risch=risch)
File "sympy/integrals/integrals.py", line 779, in doit
function = antideriv._eval_interval(x, a, b)
File "sympy/core/expr.py", line 662, in _eval_interval
B = self.subs(x, b)
File "sympy/core/basic.py", line 878, in subs
rv = rv._subs(old, new)
File "sympy/core/cache.py", line 92, in wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "sympy/core/basic.py", line 977, in _subs
rv = fallback(self, old, new)
File "sympy/core/basic.py", line 964, in fallback
arg = arg._subs(old, new, **hints)
File "sympy/core/cache.py", line 92, in wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "sympy/core/basic.py", line 977, in _subs
rv = fallback(self, old, new)
File "sympy/core/basic.py", line 969, in fallback
return self.func(*args)
File "sympy/core/cache.py", line 92, in wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "sympy/core/function.py", line 282, in __new__
result = super(Function, cls).__new__(cls, *args, **options)
File "sympy/core/cache.py", line 92, in wrapper
func_cache_it_cache[k] = r = func(*args, **kw_args)
File "sympy/core/function.py", line 128, in __new__
evaluated = cls.eval(*args)
File "sympy/functions/special/error_functions.py", line 116, in eval
t = arg.extract_multiplicatively(S.ImaginaryUnit)
File "sympy/core/expr.py", line 1852, in extract_multiplicatively
newarg = arg.extract_multiplicatively(c)
AttributeError: 'FiniteSet' object has no
attribute 'extract_multiplicatively'
P(Or(X > 2, X < 3))
1
P(And(X > 3, X > 2))
1/2
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