[Gnuplot-info] problem with fit function

[EagleFox <gri...@un...>]

I am using gnuplot to fit some experimental data. To  state more precisely:
I have for example two absorption spectra of an element, which have some
maxima and minima. Somehow one of the spectra is a bit streched but
unfortunately
not in a linear way. Therefor I calculate the exact positions of the extrema
of one spectrum and relate them to the extrema of the other spectrum.
Then I try to make a fit with gnuplot using f(x)=a*x**2 + b*x + c, in the
range form the first extremum to the last extremum (using like 10 extrema),
via a,b,c. Recalculating with the
parameters a,b,c the new x-values of the streched spectrum leads not really
to a good result. I already tried polynomals with higher order (up to 5),
but it gets worth.
Is it somehow possible to make a fit with gnuplot, so that the extrema
really are superposed?
I am really happy about any comment to that problem!
Thank you in advance!
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