Scipy’s
curve_fit()
uses iterations to search for optimal parameters. If the number of iterations exceeds the default number of 800, but the optimal parameters are still not found, then this error will be raised.
Optimal parameters not found: Number of calls to function has reached maxfev = 800
You can provide some initial guess parameters for curve_fit(), then try again. Or, you can increase the allowable iterations. Or do both!
Here is an example:
popt, pcov = curve_fit(exponenial_func, x, y, p0=[1,0,1], maxfev=5000)
p0 is the guess
maxfev is the max number of iterations
You can also try setting bounds which will help the function find the solution.
However, you cannot set bounds and a max_nfev at the same time.
popt, pcov = curve_fit(exponenial_func, x, y, p0=[1,0,1], bounds=(1,3))
Source1: https://github.com/scipy/scipy/issues/6340
Source2: My own testing and finding that the about github is not 100% accurate
Also, other recommendations about not using 0 as an ‘x’ value are great recommendations. Start your ‘x’ array with 1 to avoid divide by zero errors.