Double sigmoid fit
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Hi, I have bell-shaped data that I'd like to fit. Publications with related data use a "fit to the Boltzman equation." I imagine that this means a double sigmoid fit.
The curve fitting tool does not have a related option, any ideas would be greatly appreciated.
Thanks! Stefan
3 Comments
Andrew Newell
on 11 May 2011
See also http://www.mathworks.com/help/toolbox/stats/bq_676m-2.html#bq_676m-39.
Accepted Answer
Andrew Newell
on 11 May 2011
Here is an example of how you could use cfittool to create a sigmoid fit. First, enter these commands in the Command Window.
x = -5:.05:5;
y = tanh(x);
cfittool
In the Curve Fitting Tool, do the following:
- Click on the Data... button and import x and y.
- Click on Fitting... and then New fit.
- Under Type of fit, choose CustomEquations.
- In the New Custom Equation window, click on GeneralEquations.
- In the Equation: line after the = sign, type in a*exp(-b*x)+c, and click OK.
- Finally, click Apply to see a nicefit.
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