SAGE gave me this strange result when attempting to integrate a
piecewise-defined function:
sage: v,x=var('v,x')
sage: def chi_squared_pdf(x,v):
....: if x > 0:
....: return 1/( 2^(v/2) * gamma(v/2) ) * x^(v/2 - 1) * exp(-
x/2)
....: else:
....: return 0
....:
sage: integrate(chi_squared_pdf(x,24), x, 364/10, infinity)
0
The error goes away when I try this:
sage: def f(x,v): return 1/( 2^(v/2) * gamma(v/2) ) * x^(v/2 - 1) *
exp(-x/2)
....:
sage: integrate(f(x,24), x, 364/10, infinity)
560147352029072813039*e^(-91/5)/139218750000000
SAGE does seem to have accepted my definition of the function
chi_squared_pdf:
sage: chi_squared_pdf(364/10,24)
506240953553539690213*e^(-91/5)/556875000000000
I'm not sure why it won't integrate it. Am I doing something wrong?
Sincerely,
Greg
------------------------------------------------
| Greg Marks |
| Department of Mathematics and Computer Science |
| St. Louis University |
| St. Louis, MO 63103-2007 |
| U.S.A. |
| |
| Phone: (314)977-7206 |
| Fax: (314)977-1452 |
| Web: http://math.slu.edu/~marks |
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