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Verifying extracted curve fitting parameters.

Posted 10 years ago
Hello,

Below is my script for finding curve fitting parameters R1,R2,R3,R4,C1,C2,C3,C4.
How do I verify whether my extracted parameters are correct or not?

The script is attached below with the file name thetajc.

Thanks,
Ram
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POSTED BY: Ram K
5 Replies
Posted 10 years ago
Hey Thanks Chris! You're a rockstar! This works pretty well and the numbers seem realistic!!
You made my day! 
POSTED BY: Ram K
The outter List layer of your data was giving FindFit some heartburn. I had to remove that with First. The result of FindFit is replacement rules of the form {R1 -> val1, R2 -> val2, R3 -> val3, ...}. These rules will directly replace the matching paramaters in your model formula md1. This result I call solution numbe one, sol1. To visualize the performance of the solution, Show the data and the Plot of the fitted curve together.
sol1 = mdl /. FindFit[First@datav, mdl, RC, var]
Show[ListPlot[datav, PlotRange -> All], Plot[sol1, {t, 0, 2}, PlotStyle -> Red]]
Posted 10 years ago
Hey Chris, I had one last question. 
Is there a way I can restrict the range of the fitting variables to a predetermined range? 
e.g. let's say I want to limit the range of following variables
R1 = {0.0001,1}
R2 = {0.1,5}
R3={0.001,1}
R4={0.1,100}
C1={0.00001,0.00000001}
C2={0.0001,0.1}
C3={0.01,10}
C4={0.001,10}
Is it possible to restrict the variables in these ranges. I'm looking at the help files to figure this out!
POSTED BY: Ram K
Posted 10 years ago
In this https://reference.wolfram.com/mathematica/ref/FindFit.html
Click on Scope about half way down the page
and then click just below that on Constraints and Starting Values
to see an example showing how to restrict ranges of variables.
POSTED BY: Bill Simpson
Posted 10 years ago
Thanks Bill
POSTED BY: Ram K
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