passing arguments to a function for fitting
curve-fitting, numpy, python, scipy
Solution
A look at the documentation of `scipy.optimize.curve_fit()` is all it takes. The prototype is
scipy.optimize.curve_fit(f, xdata, ydata, p0=None, sigma=None, **kw)
The documentation states `curve_fit()` is called with the target function as the first argument, the independent variable(s) as the second argument, the dependent variable as the third argument ans the start values for the parameters as the forth argument. You tried to call the function in a completely different way, so it's not surprising it does not work. Specifically, you passed `zn` as the `p0` parameter – this is why the function was called with so many parameters.
The documentation also describes how the target function is called:
`f`: callable The model function, `f(x, ...)`. It must take the independent variable as the first argument and the parameters to fit as separate remaining arguments.
`xdata` : An `N`-length sequence or an `(k,N)`-shaped array for functions with k predictors. The independent variable where the data is measured.
You try to uses to separate arguments for the dependent variables, while it should be a single array of arguments. Here's the code fixed:
def func(x, a, b, c):
return a * np.exp(-b * (x[0] + x[1])) + c
N = 50
x = np.linspace(0,4,50)
x = numpy.array([x, x]) # Combine your `x` and `y` to a single
# (2, N)-array
z = func(x, 2.5, 1.3, 0.5)
zn = z + 0.2 * np.random.normal(size=x.shape[1])
popt, pcov = curve_fit(func, x, zn)
Problem
I am trying to fit a function which takes as input 2 independent variables x,y and 3 parameters to be found a,b,c. This is my test code: ``` import numpy as np from scipy.optimize import curve_fit def func(x,y, a, b, c): return a*np.exp(-b*(x+y)) + c y= x = np.linspace(0,4,50) z = func(x,y, 2.5, 1.3, 0.5) #works ok #generate data to be fitted zn = z + 0.2*np.random.normal(size=len(x)) popt, pcov = curve_fit(func, x,y, zn) #<--------Problem here!!!!! ``` But i am getting the error: "func() takes exactly 5 arguments (51 given)". How can pass my arguments x,y correctly?