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pb
Italy
8 Posts |
 Posted - 01/18/2002 : 11:29:38 AM
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I would like to fit a dataset using the sum of two or more fitting functions, already defined in Origin (6.0). For example, an exponential decay and a gaussian.
Do I have to re-write a new fitting function or may be there is an easy way to combine them while selecting the fitting function in the non-linear curve fit?
Thanks
Paola |
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Lorraine
USA
66 Posts |
Posted - 01/18/2002 : 1:27:48 PM
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While you cannot make permanent changes to pre-existing fitting functions in Origin, you can copy all the functions (Gaussian, ExpDecay, etc.) using CTRL-C/CTRL-V into i.e., Notepad then paste them all together into a User Defined fitting function you create on your own. This only has to be set up once, then can be saved as a User Defined Fitting function for use in future sessions of Origin. If your function starts with y= don't forget to set the form to y-script.
Lorraine
OriginLab Technical Support |
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easwar
USA
1965 Posts |
Posted - 01/21/2002 : 11:10:53 AM
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Hi Paola,
For example, to fit a gaussian with an exponential background, you can define your function
as
expdec1(x,y0,A1,t1)+gaussamp(x,0,xc,w,A)
This is a combination of the built-in functions expdec1(x,y0,A1,t1) and gaussamp(x,y0,xc,w,A). Note that both functions have an offset parameter, and in this example the offset is handled in the first function and is set to zero in the second function.
Using a combination of built-in functions will result in much faster operations in the fitter.
In the upcoming version of 7.0, we are introducing a compiler that will provide much more speed and flexibility for fitting with user-defined functions. The above approach (combining built-in functions) will of course work as well in 7.0
For more information on 7.0, please visit:
http://www.originlab.com/www/products/origin7/index.asp
Easwar
OriginLab.
Edited by - easwar on 01/21/2002 12:59:23 |
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Combine different fitting functions