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Meilongwei
China
5 Posts |
 Posted - 04/15/2015 : 01:00:30 AM
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Dear all:
I want to fit some data with my own piecewise function as follows:
y=a*x^2+b/x+c*x+d (if x>0.1)
y=a*x^2+b/(x^2+1)+c*x+d (if x<=0.1)
Here a, b, c, d are the parameters I want to calculate with origin. How do I input it in self-defined function dialog?
I tried the code as follows:
if(x>0.1)
y=a*x^2+b/x+c*x+d
else
y=a*x^2+b/(x^2+1)+c*x+d
But it could not be compiled.
Can any body help me? Thanks a lot!
Longwei
meilongwei |
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AmandaLu
439 Posts |
Posted - 04/15/2015 : 06:44:12 AM
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Hi Weilongwei,
You can define the piecewise function in OriginC. With Fitting Function Organizer opened, select Origin C for Function Form and define the fitting function in Code Builder
void _nlsfpiecewise(
double xc, double a, double b, double c, double d,
double x,
double& y)
{
if(x>xc) {
y=a*x^2+b/x+c*x+d;
}
else {
y=a*x^2+b/(x^2+1)+c*x+d;
}
}
Here is a tutorial you can follow:
http://www.originlab.com/doc/Tutorials/Fitting-Piecewise
If you define the function in Fitting Function Builder, please don't forget to put semicolon at the end of every command.
Thanks,
Amanda
OriginLab Technical Service |
Edited by - AmandaLu on 04/15/2015 06:51:15 AM |
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Meilongwei
China
5 Posts |
Posted - 04/15/2015 : 10:55:48 AM
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quote:
Originally posted by AmandaLu
Hi Weilongwei,
You can define the piecewise function in OriginC. With Fitting Function Organizer opened, select Origin C for Function Form and define the fitting function in Code Builder
void _nlsfpiecewise(
double xc, double a, double b, double c, double d,
double x,
double& y)
{
if(x>xc) {
y=a*x^2+b/x+c*x+d;
}
else {
y=a*x^2+b/(x^2+1)+c*x+d;
}
}
Here is a tutorial you can follow:
http://www.originlab.com/doc/Tutorials/Fitting-Piecewise
If you define the function in Fitting Function Builder, please don't forget to put semicolon at the end of every command.
Thanks,
Amanda
OriginLab Technical Service
Thanks a lot! It works now!
meilongwei |
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Topic |
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How to input piecewise function when fitting data