How do I extract the exponent from a semilogy plot?

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Janna Hinchliff
Janna Hinchliff on 26 Feb 2019
Commented: Stephan on 26 Feb 2019
If I use semilogy to plot some data such that the plot appears as a straight line, how can I extract the exponent of this line? Can I use polyfit to get this or is there a different way?

Accepted Answer

Stephan
Stephan on 26 Feb 2019
Edited: Stephan on 26 Feb 2019
Hi,
i think you should use lsqcurvefit (requires Optimization Toolbox) or fit (requires Curve Fitting Toolbox) - depending on the toolboxes you have access to. I would expect an exponential function if there is a straight line in the semilogy plot. Due to this polyfit is not the correct choice. I recommend to work through this examples:
lsqcurvefit:
fit:
In case of lsqcurvefit the resulting elements of solutiuon x contain the needed exponent. In case of fit you get the values with the coeffvalues function.Therefore see also Fit Postprocessing.
Best regards
Stephan
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Stephan
Stephan on 26 Feb 2019
No problem - if this was useful for you please accept my answer.

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