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sina1366
7 Posts |
 Posted - 04/27/2014 : 10:19:48 AM
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Origin Ver. and Service Release (Select Help-->About Origin):
Operating System:
Hi
I have 8 functions, 8 dependent variables (y1,y2,...,y8), 2 independent variables (x1,x2) and 7 parameters (common in all functions). I want to fit 8 curves simultaneously with 8 functions. However, y1 to y4 are dependent on x1 and y5 to y8 are dependent on x2 (0<x1<0.3 and 0<x2<0.4). As simple example:
y1 = A+B*x1
y2 = A+B*x1
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y5 = A+B*x2
y6 = A+B*x2
...
Is that possible to assign x1 to y1-y4 and x2 to y5-y8 and fit the curves? I have tried Function Form "Equations" but I couldn't get my target results!
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SeanMao
China
288 Posts |
Posted - 04/28/2014 : 05:33:15 AM
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Hi sina1366,
The Global fit function in non-linear fit (NLFit) tool in Origin will be able to help you solve the problem.
If you follow the tutorial below and set A, B as the shared parameters, you can simultaneously fit all 8 curves with different X ranges.
http://www.originlab.com/doc/Tutorials/Fitting-Global
Sean
Originlab Technical Service
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sina1366
7 Posts |
Posted - 04/29/2014 : 08:52:12 AM
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Dear Sean
Thank you very much...it was a great help to me, but I have another problem here. I have 8 different functions (not one constant function), for example:
y1 = A+B*x1+C*x1^2+...
y2 = A+B*x1^n+...
...
How can I assign function No. 1 to (x1,y1), function No. 2 to (x1,y2) and ...?
I found that if many functions are defined in global fit (y1, y2, ...), the number of plots will increase (since y1,y2,y3,... are plotted as a function of both x1 and x2)
Thanks again for your big favor...
ss |
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SeanMao
China
288 Posts |
Posted - 04/30/2014 : 12:45:57 AM
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Hi sina1366,
I sent you an email to answer your problem based on your last post along with two attached files. To fit multiple functions with multiple variables with shared parameters, Nonlinear Multiple Variables Fitting in Non-Linear Fit (NLFit) tool will be able to serve the purpose. You have to define your own multiple fitting function before you can use the tool. Below is a tutorial of how to perform the fitting:
http://www.originlab.com/doc/Tutorials/Fitting-NLFit-MultiVar
Thanks!
Sean
OriginLab Tech Service
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Fitting Multiple Datasets