[sage-support] Re: numerical evaluation of integral?

[Tim Lahey]

On Dec 4, 2008, at 9:38 PM, Jason Grout wrote:

Robert Dodier wrote:

On Dec 4, 2:04 pm, "William Stein" <[EMAIL PROTECTED]> wrote:

sage: f.n()

and get back a floating point number.  This is surprisingly not
implemented in Sage, but it isn't.
(That's basically because Maxima itself doesn't seem to have such
functionality.)

I'm guessing that f.n() just turns on the numer flag for Maxima.
numer causes any literal numbers or symbolic constants
to be replaced by floating point values. However the integrate
function is called as without numer. If you want a numerical
integration, call quad_qags or some other Quadpack function.

FYI, scipy has numerical integration, based on quadpack:

http://docs.scipy.org/doc/scipy/reference/integrate.html

sage: from scipy.integrate import quad
sage: f(x) = 250*cos(pi*x/180)^1.8 + 170.35
sage: from sage.ext.fast_eval import fast_float
sage: ff = fast_float(f, 'x')
sage: quad(ff,0,18)
(7435.2795815640284, 8.2548185859776835e-11)
sage: timeit('quad(ff,0,18)')
625 loops, best of 3: 118 µs per loop


then, use scipy.integrate.Inf.

It sounds like it would be good to use this if we wanted a numerical
approximation of an integral.

Jason

There are lots of options you can pass. If you want an infinite limit,

integral? That way, if one has tried to analytically evaluate it, they
can pull it out and try numerically evaluating it easily. In fact, it
probably could be done automatically.

Cheers,

Tim.

---
Tim Lahey
PhD Candidate, Systems Design Engineering
University of Waterloo
http://www.linkedin.com/in/timlahey

Is there an easy way to get the integrand, variable and bounds out of the

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