>> I'm attempting to fit the following equation to a set of data >> characterizing something's autocorrelation function: >> >> y=e^(a*x)^n
Your y seems to drop off exponentially, so you want the exponent to be negative, and you're raising it to a power that may not be an integer. If I change your function I can do the following to fit it:
>> myexp = fittype('exp(a*(abs(x-b)^n))') myexp = General model: myexp(a,b,n,x) = exp(a*(abs(x-b)^n)) >> fit(x,y,myexp,'start',[-20,4.47,1]) ans = General model: ans(x) = exp(a*(abs(x-b)^n)) Coefficients (with 95% confidence bounds): a = -103.6 (-115.1, -92.15) b = 4.475 (4.474, 4.475) n = 1.065 (1.035, 1.094)
While you may not want this function, I hope this illustrates what you can try with a function that you choose yourself.