CODEWITHSUNDEEP
pythoncurve-fittinggaussian
HMM
HMM

Reputation: 17

Gaussian curve fitting python

I have a problem fitting some date with Gaussian function. I tried to do it in multiple different ways but none of them worked. I need some ideas please. The data is attached (columns 2 and 3).


import pandas as pd
import matplotlib.pyplot as plt
from scipy.optimize import curve_fit
from numpy import asarray as ar,exp



x = ar(range(19))
y = ar(0, 0, 0, 0, 0, 0, 0.01955, 1.163025, 19.7159833333333, 81.3119708333334,80.0329166666667,19.3835833333333, 0.03378, 0, 0, 0, 0, 0, 0)

#y = ar(007, 0.04, .175, .628, 1.89, 4.78,10.034,17.542, 25.589, 31.1, 31.544, 26.65, 18.74, 11.01, 5.39, 2.209, 0.74, 0.215. 0.049)


n = len(x)                          
mean = sum(x*y)/n                   
sigma = sum(y*(x-mean)**2)/n        

def gaus(x,a,x0,sigma):
    return a*exp(-(x-x0)**2/(2*sigma**2))

popt,pcov = curve_fit(gaus,x,y)
#popt,pcov = curve_fit(gaus,x,y,p0=[1,mean,sigma])

plt.scatter(x,y, color='blue')
plt.plot(x,y,label='data', marker='', color='blue', linestyle='-', linewidth=2)
plt.scatter(x,gaus(y,*popt), color='red')
plt.plot(x,gaus(y,*popt),label='fit', marker='', color='Red', linestyle='--', linewidth=2)

print(len(x))
print(mean,sigma)

plt.legend()

plt.xlabel('No of Resets', fontsize=20)
plt.ylabel('Frequency', fontsize=20)

plt.legend(loc='upper right')
plt.title('Gaussian Fit', fontsize=20)

plt.show()

Upvotes: 0

Views: 368

Answers (1)

Carlos Horn
Carlos Horn

Reputation: 1293

I agree with @ddejohn.

However, you are calculating the mean and std wrongly. You could use the following approximation for the integral

import numpy as np
mean = (x*(y/y.sum())).sum()
sigma = np.sqrt(((y/y.sum())*(x-mean)**2).sum())

These should be used as initial guess for the fit as in your commented line, where you can also add a0 = y.max() for the amplitude.

popt,pcov = curve_fit(gaus,x,y,p0=[a0,mean,sigma])

Then plot as @ddejohn said maybe with more sample points

xx = np.linspace(x[0], x[-1], 100)
plt.plot(xx,gaus(xx,*popt),label='fit', marker='', color='Red', linestyle='--', linewidth=2)

Upvotes: 1

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