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Tux_Addict
France
3 Posts |
 Posted - 03/02/2012 : 06:38:05 AM
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Origin Ver.: OriginPro 8.6.0
Operating System: W7 64bits
Hi everyone,
I am trying to fit experimental data with the equation in attachment.
This equation combines an integrale and a sum.
The data represents W as a function of time (t).
I have already read the tutorials and the forum about fitting with integrale and, even if I have found plenty of interesing things, I still do not manage to proceed..
I tried to solve this equation by using a user-define function as in the tutorial. To do, I am using the code FittingWithSummation (still from the tuto).
The compilation works fine and no mistake are found but when I try to simulate, then Origin doesn't respond anymore. I have to kill him..
I am pretty sur that the matter comes from my code but I am a newbie in programming and I cannot find the solution by myself.
So if someone could help me, I would be really happy!
Thanks a lot for your help in advance!
http://www.originlab.com/ftp/forum_and_kbase/Images/equation.pdf
#include <origin.h>
// Subroutine for integrand
double f(double x, double D, double e, double n, double m, double t)
{
return exp((-0.5*(x-m)*(x-m)/e/e)-(PI*PI*n*n*D*t/x/x));
}
//----------------------------------------------------------
//
void _nlsfuptake_fit(
// Fit Parameter(s):
double D, double e, double m, double tstep, double tmax, double w,
// Independent Variable(s):
double x,
// Dependent Variable(s):
double& y)
{
// Beginning of editable part
int n=1; // variables initialization
int t=0;
do // loop over t
{
do // loop over n
{
// Set the tolerance for stop integration.
double dPrecision = 1e-12;
// Initialization
double dIntegral = 0.0;
double dTrapezia = 0.0;
// Steps, or Precision.
double dStep = 0.1e-6;
// Perform integrate by trapezoidal rule.
// Note that you should guarantee that the function is CONVERGENT.
do
{
// Trapezia area.
dTrapezia = 0.5 * ( f(x, m, e, n, D, t) + f((x+dStep), m, e, n, D, t) ) * dStep;
// Accumulate area.
dIntegral += dTrapezia; // intregral calculation.
x += dStep;
// }while( (dTrapezia/dIntegral) > dPrecision );
}while(x<10e-6);
y += 1/(n*n)*dIntegral; // sommation over n.
n=n+1;
}while (n<11);
w = 6/(e*PI*PI*sqrt(PI*2))*y; // uptake calculation.
t=t+tstep;
}while (t<tmax);
// End of editable part
}
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Tux_Addict
France
3 Posts |
Posted - 03/02/2012 : 06:59:52 AM
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Hi,
I forgot to say that "D" is the variable to fit.
"e" and "m" are constants and there values are know.
So I want to fit W=f(t) by adjusting "D".
"x" varies from 0 to infinite and "n" from 1 to infinite (but 10 is fine!).
Thanks for you help!
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Tux_Addict
France
3 Posts |
Posted - 03/05/2012 : 03:24:16 AM
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ok,so here is my new try...
Origin doesn't freeze anymore but it still doesn't work!
So if someone could help...
#include <origin.h>
// Add your special include files here.
// For example, if you want to fit with functions from the NAG library,
// add the header file for the NAG functions here.
// Subroutine for integrand
double f(double x, double D, double e, double n, double m, double t)
{
return exp((-0.5*(x-m)*(x-m)/e/e)-(PI*PI*n*n*D*t/x/x));
}
//----------------------------------------------------------
//
void _nlsfuptake_fit_3(
// Fit Parameter(s):
double D, double e, double m, double tstep, double tmax, double x,
// Independent Variable(s):
double t,
// Dependent Variable(s):
double& w)
{
// Beginning of editable part
int n=1; // variables initialization
t=0;
x=0;
// Set the tolerance for stop integration.
double y=0;
double dPrecision = 1e-12;
// Initialization
double dIntegral = 0.0;
double dTrapezia = 0.0;
// Steps, or Precision.
double dStep = 0.1e-6;
// Perform integrate by trapezoidal rule.
// Note that you should guarantee that the function is CONVERGENT.
do // loop over t
{
do // loop over n
{
do
{
// Trapezia area.
dTrapezia = 0.5 * ( f(x, m, e, n, D, t) + f((x+dStep), m, e, n, D, t) ) * dStep;
// Accumulate area.
dIntegral += dTrapezia; // intregral calculation.
x += dStep;
// }while( (dTrapezia/dIntegral) > dPrecision );
}while(x<10e-6);
y += 1/(n*n)*dIntegral; // sommation over n.
n=n+1;
}while (n<11);
t=t+tstep;
}while (t<tmax);
w = 6/(e*PI*PI*sqrt(PI*2))*y; // uptake calculation.
// End of editable part
}
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Topic |
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Fitting equation combining summation & integrale