I am writing a code that allows me to obtain the linear regression of some measures. I have used different codes but with all of them I get strange result. Instead of being a line with a constant slope, the line I get is first horizontal and between the penultimate point and the last point the slope decreases. The code I am using is:
import matplotlib.pyplot as plt
import numpy as np
x0=[0.00000001,0.000001,0.0001,0.01]
y0=[0.9974209723854539,0.9945196648709005,0.9914759279447916,0.9852556749265332]
x=np.array(x0)
y=np.array(y0)
m,b=np.polyfit(x,y,1)
print(m,b)
plt.scatter(x,y)
plt.plot(x,m*x+b,color='green')
plt.xscale('log')
d=['linear fit '+str(round(m,4))+'*x+'+str(round(b,4)),'real measure']
plt.legend(d,loc="upper right",borderaxespad=0.1,title="")
And I get the following graph: Phyton plot
Which is very different from what I should get, which I have been able to draw in Origin: Origin plot
I have tried various linear fit methods but with all of them I get this form which is wrong. Hopefully you can help me find the error. Thank you very much.