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alexxxx
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 Posted - 01/11/2007 : 09:02:47 AM
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Origin Version (Select Help-->About Origin): 7.5
Operating System:XP
Hello
At me such question: I use for fitting of a curve Peak Fitting Module.
I use there for fitting Gaussian-Functions. As constraints i need to set the certain ratio between heights of some peaks. How it can be realized in Origin?
Thank you for your help. |
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larry_lan
China
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Posted - 01/11/2007 : 10:24:34 PM
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Hi:
You can define a User-defined Gaussian function in PFM to do this:
1). Go to the Peak Finding step of PFM, click the Add/Modify button to define a new function:
2). The new Gaussian function is defined as follow, make sure to uncheck Use Area in defination.
3). Before you perform fitting, click the Parameter display button
And set constraints:
For Example, you can set the ratio between heights like:
4). In this user-define function, we have removed the parameter A (area). If you also need the value of A, you can calculate it by yourself:
Any more question about defining constraint in PFM, please read the PFM help file, which can be download from here:
http://www.originlab.com/index.aspx?s=12&lm=66&pid=612
Larry
OriginLab Technical Services
Edited by - larry_lan on 01/11/2007 10:27:22 PM |
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alexxxx
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Posted - 01/12/2007 : 09:15:51 AM
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Thank you very much! I try!
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alexxxx
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Posted - 01/13/2007 : 09:04:18 AM
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Hello!
New function works. But I had other problem. Fitting is carried out with 6 Gaussians. Between the first and third peak there should be a relation of heights equal 1.63 (H_3=1.63*H_1;). Between the second and fourth peak there should be a ratio of the areas equal 2 (A_4=2*A_2;).
1 and 3 peaks has described with "new function", the others with built-in Gaussian function.
At fitting there is a mistake: "Error! H_3 in the constraints is neither a predefined variable nor a parameter name." What to do?
And still operation of fitting with "new function" proceeds very slowly.
Edited by - alexxxx on 01/13/2007 09:06:38 AM |
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larry_lan
China
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Posted - 01/14/2007 : 8:24:45 PM
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Hi:
The variable index is base on their created sequence. For example, if there are four peaks organized by:
Peak1: user-defined Gaussian
Peak2: build-in Gaussian
Peak3: user-defined Gaussian
Peak4: build-in Gaussian
Then, the parameter names should be:
Peak1: xc_1, h_1, w_1
Peak2: xc_2, A_1, w_2
Peak3: xc_3, h_2, w_3
Peak4: xc_4, A_2, w_4
So, your constraints should be (h_2 = 1.63*h_1) and (A_2 = 2*A_1).
Larry
OriginLab Technical Services
Edited by - larry_lan on 01/14/2007 8:26:26 PM |
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Gaussian Fitting