Fitting for Complex Exponential Signal

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Hello all,

I am trying to fit my experimental data to complex exponential signal. I tried to use:

Curve Fitting -> Function -> exp
However, it seems like igor fitting function assumes only real coefficient since I could not get any meaningful fitting. Is there a way to fit complex exponential function?

I am also attaching igor file that contains data.

Thank you for your time temp1.pxp (1.6 MB)
Maybe something like this:
Function ComplexExponential(w,xx) : FitFunc
    Wave w
    Variable xx

    //CurveFitDialog/ These comments were created by the Curve Fitting dialog. Altering them will
    //CurveFitDialog/ make the function less convenient to work with in the Curve Fitting dialog.
    //CurveFitDialog/ Equation:
    //CurveFitDialog/ f(xx) = C * real(exp(cmplx(ar, ai)*xx))
    //CurveFitDialog/ End of Equation
    //CurveFitDialog/ Independent Variables 1
    //CurveFitDialog/ xx
    //CurveFitDialog/ Coefficients 3
    //CurveFitDialog/ w[0] = C
    //CurveFitDialog/ w[1] = ai
    //CurveFitDialog/ w[2] = ar

    return w[0] * real(exp(cmplx(w[2], w[1])*xx))
End

I was unable to find a good ai to match the frequency of your signal, and the fit isn't really great. But at least it's doing something... :)

John Weeks
WaveMetrics, Inc.
support@wavemetrics.com
Graph7.png (67.07 KB)

April 6, 2016 at 11:13 am - Permalink