2nd file

import matplotlib.pyplot as plt
import numpy as np
from scipy import optimize

get_ipython().run_line_magic('matplotlib', 'inline')
fig,ax = plt.subplots(figsize=(16,8))
f=np.poly1d([5,1])
x=np.linspace(0,20,30)
y=f(x)+6*np.random.normal(size=len(x))
m,c=np.polyfit(x,y,1)
xn=np.linspace(0,20,200)
yn=np.polyval([m,c],xn)
xn_1=np.linspace(0,15,200)

##see how i manipulate the position of data displayed according to the legend ur lect provided##
##it should be followed by the variable of ur plot, then the title of ur legend##
## also note that there is no label in the ax.plot, it wont conflict but to avoid confusion#
## note that there is a comma at the variable##
##it is because without that comma,the plt returns those variable as a tuple, instead of a line object##

data,=ax.plot(x,y,"ob")
polyfit,=ax.plot(xn,yn,color="black")
ntg,=ax.plot(x,y)
polyfit12,=ax.plot(xn_1,yn,"red")
ax.legend((polyfit12,polyfit,ntg,data),(["Linear fit first 12 points","Linear fit first 20 points","polynomial fit","datapoints"]),ncol=2)