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cyberjuda
Germany
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Posted - 05/29/2009 : 06:17:41 AM
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Origin Ver. 8 and Service Release 4(Select Help-->About Origin): Operating System: Windows XP Professional
I can't seem to able to use this function as a fit function. Any basic help in the right direction would be appreciated.
where T, t, a and b are variables whereas c, d are constants.
I have read through the wiki but can't seem to find anything I can use specifically for this problem.
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Echo_Chu
China
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cyberjuda
Germany
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Posted - 06/02/2009 : 05:13:16 AM
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Thank you for the help. I have been able to change the code from one of the tutorials to fit my equation but it doesn't seem to work. Can you please look at the code and see if everything is in order. Oh and I also attach the new form of the equation that I am using. I am able to simulate it correctly but when I try to fit it, it gives me an error that "Fit did not converge - reason unknown." The edits that I made to the code concerns the part where the integral is given and then in the second last line I added the part before the integral. I think the problem might be related to the limits of the integration but don't know how to edit that.
#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.
#include <oc_nag8.h>
// Add code here for other Origin C functions that you want to define in this file,
// and access in your fitting function.
struct user // parameters in the integrand
{
double amp, center, width;
};
// Function supplied by user, return the value of the integrand at a given x.
static double NAG_CALL f_callback(double x, Nag_User *comm)
{
struct user *sp = (struct user *)(comm->p);
double amp, center, width; // temp variable to accept the parameters in the Nag_User communication struct
amp = sp->amp;
center = sp->center;
width = sp->width;
return amp * exp(x/(0.8))*exp(-center/(8.314*x))*exp((-width*8.314*x*x*exp(-center/(8.314*x)))/(0.4*center));
}
// You can access C functions defined in other files, if those files are loaded and compiled
// in your workspace, and the functions have been prototyped in a header file that you have
// included above.
// You can access NLSF object methods and properties directly in your function code.
// You should follow C-language syntax in defining your function.
// For instance, if your parameter name is P1, you cannot use p1 in your function code.
// When using fractions, remember that integer division such as 1/2 is equal to 0, and not 0.5
// Use 0.5 or 1/2.0 to get the correct value.
// For more information and examples, please refer to the "User-Defined Fitting Function"
// section of the Origin Help file.
//----------------------------------------------------------
//
void _nlsfPW(
// Fit Parameter(s):
double y0, double A, double xc, double w,
// Independent Variable(s):
double x,
// Dependent Variable(s):
double& y)
{
// Beginning of editable part
// Through the absolute accuracy epsabs, relative accuracy epsrel and max_num_subint you can
// control the precision of the integration you need
// if epsrel is set negative, the absolute accuracy will be used.
// Similarly, you can control only relative accuracy by set the epsabs negative
double epsabs = 0.0, epsrel = 0.0001;
// The max number of sub-intervals needed to evaluate the function in the integral
// The more diffcult the integrand the larger max_num_subint should be
// For most problems 200 to 500 is adequate and recommmended
Integer max_num_subint = 200;
// Result keeps the approximate integral value returned by the algorithm
// abserr is an estimate of the error which should be an upper bound for the |I - result|
// where I is the integral value
double result, abserr;
// The structure of type Nag_QuadProgress,
// it contains pointers allocated memory internally with max_num_subint elements
Nag_QuadProgress qp;
// The NAG error parameter (structure)
static NagError fail;
// Parameters passed to integrand by Nag_User communication struct
Nag_User comm;
struct user s;
s.amp = A;
s.center = xc;
s.width = w;
comm.p = (Pointer)&s;
// Perform integration
// There are 3 kinds of infinite boundary types you can use in Nag infinite integrator
// Nag_LowerSemiInfinite, Nag_UpperSemiInfinite, Nag_Infinite
d01smc(f_callback, Nag_LowerSemiInfinite, x, epsabs, epsrel, max_num_subint, &result, &abserr, &qp, &comm, &fail);
// you may want to exam the error by printing out error message, just uncomment the following lines
// if (fail.code != NE_NOERROR)
// printf("%s\n", fail.message);
// For the error other than the following three errors which are due to bad input parameters
// or allocation failure NE_INT_ARG_LT NE_BAD_PARAM NE_ALLOC_FAIL
// You will need to free the memory allocation before calling the integration routine again to avoid memory leakage
if (fail.code != NE_INT_ARG_LT && fail.code != NE_BAD_PARAM && fail.code != NE_ALLOC_FAIL)
{
NAG_FREE(qp.sub_int_beg_pts);
NAG_FREE(qp.sub_int_end_pts);
NAG_FREE(qp.sub_int_result);
NAG_FREE(qp.sub_int_error);
}
// Calculate the fitted value
y = y0 + exp(-x/0.8)*w/0.4*result;
// End of editable part
} |
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cyberjuda
Germany
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Posted - 06/03/2009 : 03:51:11 AM
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I realized that I have been using the wrong tutorial. Well my fit function is finally working. Here is the code and the equation in case it helps someone else. Just another question though. Is it possible to modify this code so that I can use it to fit multiple peaks? The function would simply be a summation for all the peaks. If someone can again point me in the right direction, it would be highly appreciated.
a=w b=xc [Edit] I forgot to mention that in the parameter options I had to set c=0 and d is the Amplification factor.
#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.
#include <oc_nag8.h>
// Add code here for other Origin C functions that you want to define in this file,
// and access in your fitting function.
struct user
{
double a, b, fitX; // fitX the independent variable of fitting function
};
static double NAG_CALL f_callback(double x, Nag_User *comm) // x is the independent variable of the integrand
{
struct user *sp = (struct user *)(comm->p);
double aa, bb, fitX; // temp variable to accept the parameters in the Nag_User communication struct
aa = sp->a;
bb = sp->b;
fitX = sp->fitX;
return exp(fitX/(0.8))*exp(-bb/(8.314*fitX))*exp((-aa*8.314*fitX*fitX*exp(-bb/(8.314*fitX)))/(0.4*bb));
}
// You can access C functions defined in other files, if those files are loaded and compiled
// in your workspace, and the functions have been prototyped in a header file that you have
// included above.
// You can access NLSF object methods and properties directly in your function code.
// You should follow C-language syntax in defining your function.
// For instance, if your parameter name is P1, you cannot use p1 in your function code.
// When using fractions, remember that integer division such as 1/2 is equal to 0, and not 0.5
// Use 0.5 or 1/2.0 to get the correct value.
// For more information and examples, please refer to the "User-Defined Fitting Function"
// section of the Origin Help file.
//
//----------------------------------------------------------
//
void _nlsfPWwithparametric(
// Fit Parameter(s):
double a, double b, double c, double d,
// Independent Variable(s):
double x,
// Dependent Variable(s):
double& y)
{
// Beginning of editable part
double epsabs = 0.00001, epsrel = 0.0000001, result, abserr;
Integer max_num_subint = 500;
// you may use epsabs and epsrel and this quantity to enhance your desired precision
// when not enough precision encountered
Nag_QuadProgress qp;
static NagError fail;
// the parameters parameterize the integrand can be input to the call_back function
// through the Nag_User communication struct
Nag_User comm;
struct user s;
s.a = a;
s.b = b;
s.fitX = x;
comm.p = (Pointer)&s;
d01sjc(f_callback, c, s.fitX, epsabs, epsrel, max_num_subint, &result, &abserr, &qp, &comm, &fail);
// you may want to exam the error by printing out error message, just uncomment the following lines
// if (fail.code != NE_NOERROR)
// printf("%s\n", fail.message);
// For the error other than the following three errors which are due to bad input parameters
// or allocation failure NE_INT_ARG_LT NE_BAD_PARAM NE_ALLOC_FAIL
// You will need to free the memory allocation before calling the integration routine again to
// avoid memory leakage
if (fail.code != NE_INT_ARG_LT && fail.code != NE_BAD_PARAM && fail.code != NE_ALLOC_FAIL)
{
NAG_FREE(qp.sub_int_beg_pts);
NAG_FREE(qp.sub_int_end_pts);
NAG_FREE(qp.sub_int_result);
NAG_FREE(qp.sub_int_error);
}
y = d*(exp(-x/0.8))*(a/0.4)*result;
// End of editable part
} |
Edited by - cyberjuda on 06/03/2009 03:54:33 AM |
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Echo_Chu
China
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cmohan76
India
1 Posts |
Posted - 12/11/2009 : 09:00:32 AM
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can any one help me in fitting data using the function
where gamma(0)and "a" are constant
can some generate a user define function for NLSFit fitting the data |
Edited by - cmohan76 on 12/11/2009 09:04:18 AM |
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larry_lan
China
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