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Evrim Umut
Turkey
3 Posts |
 Posted - 02/02/2011 : 10:05:27 AM
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Hello
I am using Origin V8 in a Windows7 system.
I asked this question also in Origin C topic but I couldnt managed according to instructions.
I want to fit my data with a function:
y=a1 + a2/(x-a3)
where I want to draw y vs 1/(x-a3), make the fit, and after the fit origin gives me a1,a2 and a3. Here a3 is really crusial. |
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easwar
USA
1965 Posts |
Posted - 02/02/2011 : 11:05:52 AM
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Hi Evrim,
So you want to perform an apparent linear fit to y versus 1/(x-a3) but your a3 is not known yet, and needs to be determined?
This would require some custom iterative coding, and cannot be done I think by simply defining a fitting function. You may need to do a loop where you pick an initial value of a3, transform your x values to 1/(x-a3), do a linear fit of y versus the 1/(x-a3), then adjust your a3, do the linear fit again, and repeat till you get some optimal value of a3 that give say a minimum for the r^2 of your linear fit.
But why do you have to do it this way? Why not just plot y versus x, and fit that with the nonlinear equation of
y=a1+a2/(x-a3)
and find the optimal a3 value that way using the nonlinear fitter?
Then, if you want, you can transform the x values of the data and the fit curve with that optimal value of a3 and plot the result as a linear curve if you want the graph to look linear?
Easwar
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fittin a function