
Re: Numerical integration with maxima
Posted:
Nov 6, 2012 1:54 PM


>>>>> "C" == Claude <claude@nospam.invalid> writes:
Just a couple of notes:
C> I've defined the function C> f=abs(sin(x))
Use either:
f:abs(sin(x));
or:
f(x):=abs(sin(x));
C> integrate(f, x, 0, 2*pi)
Use 2*%pi.
C> But now I don't know how to numerically evaluate this integral.
More importantly, integrate() is for symbolic integration. For numerical integration use quad_qag() and the related functions.
Try:
quad_qag(abs(sin(x)), x, 0, 2*%pi, 2);
for a 2nd order approximation. I get the result:
[4.0, 4.440892098500626e14, 63, 0]
the values in the list are theapproximation, the approx error, the number of evaluations and an error code. 0 means no error. So the result is 4.0 + 4.440892098500626e14.
Try:
? quad_qag
and:
?? QUADPACK
in maxima.
Or read the QUADPACK sections of the info or printable manual.
JimC  James Cloos <cloos@jhcloos.com> OpenPGP: 1024D/ED7DAEA6

