matlab - Rational function curve fitting in python -


i trying fit curve x , y data points using rational function. can done in matlab using cftool (http://de.mathworks.com/help/curvefit/rational.html). however, looking same in python. have tried use scipy.optimize.curve_fit, requires function, don't have.

you have function, rational function. need set function , perform fitting. curve_fit requires supply arguments not lists, supplied additional function fitting on specific case of third degree polynomial in both numerator denominator.

def rational(x, p, q):     """     general rational function description.     p list polynomial coefficients in numerator     q list polynomial coefficients (except first one)     in denominator     first coefficient of denominator polynomial fixed @ 1.     """     return np.polyval(p, x) / np.polyval([1] + q, x)  def rational3_3(x, p0, p1, p2, q1, q2):     return rational(x, [p0, p1, p2], [q1, q2])  x = np.linspace(0, 10, 100)   y = rational(x, [-0.2, 0.3, 0.5], [-1.0, 2.0]) ynoise = y * (1.0 + np.random.normal(scale=0.1, size=x.shape)) popt, pcov = curve_fit(rational3_3, x, ynoise, p0=(0.2, 0.3, 0.5, -1.0, 2.0)) print popt  plt.plot(x, y, label='original') plt.plot(x, ynoise, '.', label='data') plt.plot(x, rational3_3(x, *popt), label='fit')

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