integration problem

[Erin Hodgess]

Hello!

I'm having a little trouble with some integration.

My goal is to set up a cumulative distribution for some functions.  The one below is my attempt at the gamma distribution.  However, it does not like the integrate statement.




>>> x, y, t = symbols('x y t')
>>> shape = float(4.0)
>>> scale = float(1.5)
>>> z2 = (scale**shape)*gamma(shape)
>>> y = ((x*(shape-1))*exp(-x/scale))/z2
>>> y
0.0987654320987654*x*exp(-0.666666666666667*x)
>>> integrate(y,(x,0,t))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/sympy/utilities/decorator.py", line 30, in threaded_func
    return func(expr, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sympy/integrals/integrals.py", line 1626, in integrate
    risch=risch, manual=manual)

Has anyone run into this before, please?

Thanks in advance for any help.

Sincerely,
Erin

[Aaron Meurer]

This was a bug and has been fixed in the development version. It will
work in the next version.

Aaron Meurer

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[Erin Hodgess]

Thank you!

[mario]

I get the same error message, using the development version; putting instead

shape = 4
scale = 2

(not float) it does not give an error.

[Erin Hodgess]

Mario....that's it.  The gamma function only wants integers.

Thanks!

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Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm....@gmail.com