In [1]:

    

import numpy as np
import matplotlib
matplotlib.use('nbagg')
import matplotlib.pyplot as plt
import scipy as sp 
from scipy.special import erf 
import math as mt


    

In [2]:

    

x,y,err = np.loadtxt('Example_chi2.txt', delimiter=';')


    

In [3]:

    

plt.errorbar(x,y,err,fmt='o',color='r')
plt.errorbar(x,y,err,fmt='o',color='r')
plt.xlim(-1,10)
plt.show()


    

In [4]:

    

arr_a = np.linspace(-1,5,61)
arr_b = np.linspace(-1,5,61)
arr_c = np.linspace(-1,5,61)
arr3D = np.zeros((61,61,61))

for indexA in range(0,len(arr_a)):
    for indexB in range(0,len(arr_b)):
        for indexC in range(0,len(arr_c)):
            ymod = arr_a[indexA] * np.power(x,2) + arr_b[indexB] * x + arr_c[indexC]
            arr3D[indexA,indexB,indexC] = np.sum(np.power(ymod - y,2)/np.power(err,2))


    

In [5]:

    

tmin = np.unravel_index(arr3D.argmin(),arr3D.shape)

plt.pcolormesh(arr_a, arr_b, np.transpose(np.log10(arr3D[:,:,tmin[2]])),cmap='coolwarm')

plt.colorbar()


    

    
Out[5]:





<matplotlib.colorbar.Colorbar at 0x7f16877f8be0>

In [6]:

    

plt.pcolormesh(arr_a, arr_b, np.transpose(np.log10(arr3D[:,tmin[1],:])),cmap='coolwarm')
plt.colorbar()


    

    
Out[6]:





<matplotlib.colorbar.Colorbar at 0x7f16877c9a90>

In [7]:

    

plt.pcolormesh(arr_a, arr_b, np.transpose(np.log10(arr3D[tmin[0],:,:])),cmap='coolwarm')
plt.colorbar()


    

    
Out[7]:





<matplotlib.colorbar.Colorbar at 0x7f16877a6f28>

In [101]:

    

arr_a[tmin[0]],arr_b[tmin[1]],arr_c[tmin[2]]


    

    
Out[101]:





(-0.29999999999999993, 3.0, 1.2000000000000002)

In [102]:

    

plt.errorbar(x,y,err,fmt='o',color='r')
plt.plot(x,arr_a[tmin[0]] * np.power(x,2) + arr_b[tmin[1]] * x + arr_c[tmin[2]],color='b')
plt.xlim(-1,10)
plt.show()


    

In [103]:

    

a, b, c  = np.polyfit(x, y, 2,  w=1/err)
plt.errorbar(x,y,err,fmt='o',color='r')
plt.xlim(-1,10)
plt.plot(x, a*np.power(x,2) + b*x + c, '-')


    

    
Out[103]:





[<matplotlib.lines.Line2D at 0x7f4fb7115978>]






    

In [59]:

    

a = -0.3 b=2.6 c=4


    

    




  File "<ipython-input-59-b413a519ffff>", line 1
    a = -0.3 b=2.6 c=4
             ^
SyntaxError: invalid syntax

In [9]:

    

levels=[8.18,14.35,21.8]
plt.contour(arr_a, arr_b, np.transpose(arr3D[tmin[0],:,:]),levels)
plt.plot(arr_b[tmin[1]], arr_c[tmin[2]], 'o')
plt.ylabel(r'$b$', fontsize=20)
plt.xlabel(r'$c$',fontsize=20)
plt.show()
# plt.contour(arr_a, arr_b, np.transpose(arr3D[:,tmin[1],:]),levels)
# plt.plot(arr_b[tmin[0]], arr_c[tmin[2]], 'o')
# plt.show()
# plt.contour(arr_a, arr_b, np.transpose(arr3D[:,:,tmin[2]]),levels)
# plt.plot(arr_b[tmin[0]], arr_c[tmin[1]], 'o')
# plt.show()


    

In [71]:

    

arr_a = np.linspace(-1,5,61)
arr_b = np.linspace(-1,5,61)
arr2D = np.zeros((61,61,61))

for indexA in range(0,len(arr_a)):
    for indexB in range(0,len(arr_b)):
            ymod = arr_a[indexA] * x + arr_b[indexB]
            arr2D[indexA,indexB] = np.sum(np.power(ymod - y,2)/np.power(err,2))
            
tmin1 = np.unravel_index(arr2D.argmin(),arr2D.shape)

plt.pcolormesh(arr_a, arr_b, np.transpose(np.log10(arr2D[:,:,tmin1[2]])),cmap='coolwarm')
plt.colorbar()
plt.show()


    

In [72]:

    

arr_a[tmin1[0]],arr_b[tmin1[1]]


    

    
Out[72]:





(0.30000000000000004, 5.0)

In [75]:

    

plt.errorbar(x,y,err,fmt='o',color='r')
plt.plot(x,arr_a[tmin1[0]] * x + arr_b[tmin1[1]],color='b')
plt.xlim(-1,10)
plt.show()


    

In [82]:

    

levels=[8.18,14.35,21.8]
plt.contour(arr_a, arr_b, np.transpose(arr3D[tmin1[0],:]),levels)
plt.show()
plt.contour(arr_a, arr_b, np.transpose(arr3D[:,tmin1[1]]),levels)
plt.show()