Comment #4 on issue 2128 by jagermeistermeister: cannot integrate piecewise
function numerically
http://code.google.com/p/sympy/issues/detail?id=2128
Oops, found an error already, where can I post a bug report regarding
Mateusz's polys11 branch? Should I just put it here?
Just in case:
a = 0.00320838027923401*Piecewise((0, x < -81.7692307692308),
(1.33179680150517 - 0.015898400752587*x, x < 2),
(Piecewise((0.400000000000000, 2 < x), (0.600000000000000, True)) +
Piecewise((0.300000000000000, 123 < x), (0.700000000000000, True)), x <=
123), (2.09276729559748 - 0.0080712788259958*x, x < 382.285714285714), (0,
True))
b = -0.0139529089323533*Piecewise((0, x < 1.53846153846154), (-2.925 +
0.845000000000001*x, x < 5), (Piecewise((0.400000000000000, 5 < x),
(0.600000000000000, True)) + Piecewise((0.300000000000000, 10 < x),
(0.700000000000000, True)), x <= 10), (16.5 - 1.54*x, x <
20.7142857142857), (0, True))
integrate(a.subs(x, x-y) * b.subs(x, y), (y, -oo, oo)) gives an error
Traceback (most recent call last):
File "test.py", line 3, in <module>
t = sympy.integrate(a.subs(x, x-y) * b.subs(x, y), (y, -oo, oo))
File "/usr/local/lib/python2.6/dist-packages/sympy/utilities/decorator.py",
line 22, in threaded_decorator
return func(expr, *args, **kwargs)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 545, in integrate
return integral.doit(deep = False)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 152, in doit
antideriv = self._eval_integral(function, x)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 283, in _eval_integral
return f._eval_integral(x)
File "/usr/local/lib/python2.6/dist-packages/sympy/functions/elementary/piecewise.py",
line 153, in _eval_integral
return Piecewise(*[(integrate(e, x), c) for e, c in self.args])
File "/usr/local/lib/python2.6/dist-packages/sympy/utilities/decorator.py",
line 22, in threaded_decorator
return func(expr, *args, **kwargs)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 545, in integrate
return integral.doit(deep = False)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 152, in doit
antideriv = self._eval_integral(function, x)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 283, in _eval_integral
return f._eval_integral(x)
File "/usr/local/lib/python2.6/dist-packages/sympy/functions/elementary/piecewise.py",
line 153, in _eval_integral
return Piecewise(*[(integrate(e, x), c) for e, c in self.args])
File "/usr/local/lib/python2.6/dist-packages/sympy/utilities/decorator.py",
line 22, in threaded_decorator
return func(expr, *args, **kwargs)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 545, in integrate
return integral.doit(deep = False)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 152, in doit
antideriv = self._eval_integral(function, x)
File "/usr/local/lib/python2.6/dist-packages/sympy/integrals/integrals.py",
line 290, in _eval_integral
poly = f.as_poly(x)
File "/usr/local/lib/python2.6/dist-packages/sympy/core/basic.py", line
651, in as_poly
poly = Poly(self, *gens, **args)
File "/usr/local/lib/python2.6/dist-packages/sympy/polys/polytools.py",
line 98, in __new__
return cls._from_expr(rep, opt)
File "/usr/local/lib/python2.6/dist-packages/sympy/polys/polytools.py",
line 206, in _from_expr
return cls._from_dict(rep, opt)
File "/usr/local/lib/python2.6/dist-packages/sympy/polys/polytools.py",
line 151, in _from_dict
domain, rep = construct_domain(rep, opt=opt)
File "/usr/local/lib/python2.6/dist-packages/sympy/polys/constructor.py",
line 200, in construct_domain
result = _construct_composite(coeffs, opt)
File "/usr/local/lib/python2.6/dist-packages/sympy/polys/constructor.py",
line 148, in _construct_composite
numer[monom] = ZZ.from_sympy(coeff)
File "/usr/local/lib/python2.6/dist-packages/sympy/polys/domains/pythonintegerring.py",
line 34, in from_sympy
raise CoercionFailed("expected an integer, got %s" % a)
sympy.polys.polyerrors.CoercionFailed: expected an integer, got
-6.01396293236025e-7
For the sake of readability, a and b in pretty print look like this:
a:
0.00320838027923401⋅⎧ 0 for x <
-81.7692307692308
⎪
⎪1.33179680150517 - 0.015898400752587⋅x for x
< 2
⎪
⎪ ⎧0.4 for 2 < x + ⎧0.3 for 123 < x for x
≤ 123
⎨ ⎨ ⎨
⎪ ⎩0.6 otherwise ⎩0.7 otherwise
⎪
⎪2.09276729559748 - 0.0080712788259958⋅x for x <
382.285714285714
⎪
⎩ 0
otherwise
b:
-0.0139529089323533⋅⎧ 0 for x <
1.53846153846154
⎪
⎪ -2.925 + 0.845000000000001⋅x for x < 5
⎪
⎪⎧0.4 for 5 < x + ⎧0.3 for 10 < x for x ≤ 10
⎨⎨ ⎨
⎪⎩0.6 otherwise ⎩0.7 otherwise
⎪
⎪ 16.5 - 1.54⋅x for x <
20.7142857142857
⎪
⎩ 0 otherwise
The problem with integrate(f, (x, -oo, oo)) is gone and works perfectly
with Mateusz's branch, though. And fast, too! :)
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