From help-octave-request at bevo dot che dot wisc dot edu Tue Aug 14 09:06:25 2001
Subject: Re: problem with fsolve
From: geraint dot p dot bevan dot itar at jsfmail dot p dot external dot lmco dot com
To: "N.D.vanForeest" <foreest at math dot utwente dot nl>
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Tue, 14 Aug 2001 09:02:58 -0500

On Tue, 14 Aug 2001, N.D.vanForeest wrote:

> Hi,
>
> I would like to use fsolve to solve an equation of the type f(x;a)==0,
> where x is the variable that needs to be found, and a is a vector of
> parameters. For instance,
>
> function y = solve_rho(x)
>   y(1) = x(1)*theta +log(1-x(1)*ksi);
> endfunction
>
> Clearly I would like to pass the values of theta and ksi to the
function
> solve_rho, but without declaring them as global. Does anyone know how to
> do this? (As far as I understand the manual does not say anything about
> this.)
>

Hi,

if you don't mind using some global parameters, the simplest way of doing
this (that I know of) is to use a wrapper function to call fsolve:


	## function to evaluate
	function y = solve_rho(x,theta,ksi)
	  y(1) = x(1)*theta + log(1-x(1)*ksi)
	endfunction


	## wrapper functions
	function f = call_solve_rho(x)
	  global fsolve_parameters;
	  theta = fsolve_parameters(1);
	  ksi   = fsolve_parameters(2);
	  f = solve_rho(x,theta,ksi);
	endfunction

	function f = fsolve_par(func,x,parameters)
	  global fsolve_parameters;
	  fsolve_parameters=parameters;
	  f = fsolve(func,x);
	endfunction


	## function call
	fsolve_par("call_solve_rho",[1],[2.0;3.0])


If you are determined not to use any global variables at all, it will
probably be necessary to edit src/DLD-FUNCTIONS/fsolve.cc.

-- 
Regards,
Geraint



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