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mccx
Turkey
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 Posted - 12/04/2003 : 04:34:17 AM
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I would like to fit a dataset using the sum of two fitting functions, an exponential decay and exponential grow. y=a*exp(-k1*x)+b*(1-exp(-k2*(x-x0)). But if x equal or smaller than x0 only first function must be active. if x bigger than x0 both functions must be active. Can this type of fit be made in Origin?
Thanks. |
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easwar
USA
1965 Posts |
Posted - 12/04/2003 : 2:54:24 PM
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Hi,
Yes, you can perform this kind of fitting.
You can write your fitting equation as:
if(x<x0) y=a*exp(-k1*x);
else y=a*exp(-k1*x)+b*(1-exp(-k2*(x-x0)));
where your fitting parameters are a, k1, b, k2, and x0.
If you are using versions prior to 7, set the Form drop-down list on your function edit page to Y-script. If you have version 7 or higher, you can keep the equation the same, but leave the "Use Origin C" check box checked and it will work fine.
Easwar
OriginLab.
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two function fitting