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Dr.S
Austria
1 Posts |
 Posted - 01/07/2019 : 08:24:42 AM
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Dear all,
I am not too familiar with origin C but i tried my best in order to fit some data with a sum function based on cranks laws of diffusion.
I would like to fit the following function to my data:
y = M (1-8/pi²*SUM(1/(2n+1)² * e^(-(2n+1)²*pi²*D*x/h²) )
where the SUM is the Sum operator with n=0 to n =xx (fixed value, tried it with 5).
In order to fit the function, I programmed the following function:
--------------------------------------
#pragma numlittype(push, TRUE)
#pragma warning(error : 15618)
#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.
// Add code here for other Origin C functions that you want to define in this file,
// and access in your fitting function.
// 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 _nlsfSUM_Drying(
// Fit Parameter(s):
double D,
// Independent Variable(s):
double x,
// Dependent Variable(s):
double& y)
{
const double M=10410;
const double h=0.0015;
const double p=3.14159;
const double n=5;
// Beginning of editable part
double bb = 0;
for(int ii =1; ii<=n; ii++)
{
bb = (1/(2 * ii + 1)^2) * exp(- (2 * ii +1)^2 * p^2 * D * x / h^2 + bb);
}
y = M *(8/p^2)* bb;
// End of editable part
}
------------------------------------------------
however, fitting does not work and when I try out the function with a fixed value, the result is always 0.
Is there someone who can help me fixing it and make it work?
Thank you very much for your help.
Best regards,
Stefan
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Edited by - Dr.S on 01/07/2019 08:26:30 AM |
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yuki_wu
896 Posts |
Posted - 01/07/2019 : 9:40:20 PM
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Hi Stefan,
It seems that you made some mistakes when you wrote the function in the code, for example:
y = M *(8/p^2)* bb;
“1-” is missing.
You need to double check your code.
Regards,
Yuki
OriginLab
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Fitting function for drying