Origin Ver. 8.0 and Service Release (Select Help-->About Origin):
Operating System:windows 7
I tried to do the fit using the function
Cv=a9Nk_B #12310;(x/#952;D)#12311;^3 #8747;_0^(#952;/x)#9618;#12310;dx (x^4 * e^x)/#12310;((e^x)-1)#12311;^2 #12311;
I have written the program and compiled it. The compilation was successful. But I could not do the fitting using the function.
Can anyone tell what is the problem? Thank you very much.
ps: The function is given the end as a image.
Define the Function
Press F9 to open the Fitting Function Organizer and then create a new Category named FittingWithIntegral. Define a new fitting function nag_integration_fitting in the new category as follow:
Function Name: nag_integration_fitting
Function Type: User-Defined
Independent Variables: x
Dependent Variables: y
Parameter Names: a
Function Form: Origin C
Function:
Click the button (icon) beside the Function box to open the code builder and define and compile and save the fitting function as follows:
#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 cons;
};
// 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 cons; // temp variable to accept the parameters in the Nag_User communication struct
cons = sp->cons;
return (x*x*x*x*exp(x))/((exp(x)-1)*(exp(x)-1));
}
// 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 _nlsfnag_integration_fitting(
// Fit Parameter(s):
double a,
// 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 = 300;
// 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.cons = a;
// 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, 0, 444/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 = a*5.75*100000*(x/444)*(x/444)*(x/444)*result;
// End of editable part
}
PRATHI |
Fitting using integral
Posted - 03/03/2014 : 02:34:41 AM
