python matplotlib fitting a straight line

 

import numpy as np
import matplotlib.pyplot as plt

plt.rcParams['font.family'] = ['sans-serif']
plt.rcParams['font.sans-serif'] = ['SimHei']

def linear_regression(x, y):
    N = len (x)
    sumx = sum(x)
    sumy = sum(y)
    sumx2 = sum(x ** 2)
    sumxy = sum(x * y)
    A = np.mat([[N, sumx], [sumx, sumx2]])
    b = np.array([sumy, sumxy])
    return np.linalg.solve(A, b)

# Cantilever 
# modify data. 1: 
the X1 = np.array ([0,20,40,60,80,100,120,140,160,180,200 ])
Y1=np.array([0,0.02,0.06,0.1,0.13,0.16,0.19,0.22,0.245,0.278,0.3])

# Half-bridge 
# modify the data 2: 
an X2 = np.array ([0,20,40,60,80,100,120,140,160,180,200 ])
Y2=np.array([0,0.057,0.118,0.185,0.245,0.308,0.376,0.425,0.488,0.544,0.58])

A0, A1 = linear_regression (the X1, Yl)
 # generated line fit the plotted points 
_x1 = [0, 200 is ]
_Y1 = [a0 + a1 * x for x in _X1]

A0, A1 = linear_regression (an X2, Y2)
 # generates a fitted line of plotted points 
_X2 = [0, 200 is ]
_Y2 = [a0 + a1 * x for x in _X1]


# Display image 
plt.plot (the X1, Yl, ' RO ' , as linewidth = 2, label = " Wheatstone bridge " )
plt.plot (_x1, _y1, ' B ' , as linewidth = 2, label = ' Wheatstone bridge ' , Color = ' C0 ' )
plt.plot (an X2, Y2, ' G ^ ' , as linewidth = 2, label = ' half bridge ' )
plt.plot(_X2, _Y2, 'b', linewidth=2,label='半桥',color='C1')
plt.xlabel('weight/g')
plt.ylabel('voltage/v')
plt.legend ()
plt.show()