turn plot into a polyfit or polyval

Like to make this into polyval or polyfit so the points smooth out any noise

tried to use code, but seems it does not like taking a polyval of a FRF.

Any suggestions would help!

[dpb]

I presume FRF must be "Frequency Response Function", but how was it computed/where did it come from?

But, the problem in the above code is you've commented out the polyfit that is needed to compute a set of coefficients to pass to polyval and then just tried to use polyval on the x,y values of the to-be-fitted data instead.

The commented-out polyval line would be somewhat closer if hadn't commented out the polyfit, but it would then need to be

q=polyfit(f,abs(FRF),7);
z=polyval(q,f);

However, I'll note that a high-order polynomial such as this is highly unlikely to be satisfactory solution to the problem; you'll be wanting to look at some smoothing algorithm instead. Just what might be most appropriate would depend on what the actual data looks like which we do not have available to us.

Answer 1

[Cris LaPierre]

In your figure window, select Tools > Basic Fitting

Use the UI to find an appropriate fit to your data. Once done, export the results to the workspace.

See here: https://www.mathworks.com/help/matlab/data_analysis/interactive-fitting.html