From help-request at octave dot org Fri Aug 26 11:11:21 2005
Subject: Re: Integrating a function with many arguments over one varible.
From: "Henry F. Mollet" <mollet at pacbell dot net>
To: <mgarciad at cajadeavila dot es>, Octave_post <help@octave.org>
Date: Fri, 26 Aug 2005 09:09:42 -0700

Not sure if this helps but Octave-forge does have quadl.
Henry
octave:2> help quadl
quadl is the user-defined function from the file
/usr/local/share/octave/2.1.71/site/m/octave-forge/general/quadl.m

QUADL  Numerically evaluate integral using adaptive
  Lobatto rule.

  Q=QUADL('F',A,B) approximates the integral of
  F(X) from A to B to machine precision.  'F' is a
  string containing the name of the function. The
  function F must return a vector of output values if
  given a vector of input values.

  Q=QUADL('F',A,B,TOL) integrates to a relative
  error of TOL.

  Q=QUADL('F',A,B,TOL,TRACE) displays the left
  end point of the current interval, the interval
  length, and the partial integral.

  Q=QUADL('F',A,B,TOL,TRACE,P1,P2,...) allows
  coefficients P1, ... to be passed directly to the
  function F:  G=F(X,P1,P2,...). To use default values
  for TOL or TRACE, one may pass the empty matrix ([]).

W. Gander and W. Gautschi, Adaptive Quadrature - Revisited,
BIT Vol. 40, No. 1, March 2000, pp. 84--101.
http://www.inf.ethz.ch/personal/gander/





on 8/26/05 4:14 AM, mgarciad at cajadeavila dot es at mgarciad@cajadeavila.es
wrote:

> I need to find the integral of f(x, y1, ..., yn), over the variable x,
> between 2 limits. I read that quadl in Matlab can do it simply, you only
> have to add the values of the parameters y1, ..., yn at the end, when you
> use quadl. I tried to do the same with quad in Octave, but it did not
> work.
>  
> I can't define "by hand" a function g(x) so that g(x) = f(x, y1, ..., yn),
> and use quad with g(x), because in fact I need to find the values
> y1,...,yn that minimize such quadrature along x.
>  
> Can someone help me?
>  
> Thank you.




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