cost_function.py

import matplotlib.pyplot as plt

x = [1, 2, 3]
y = [1, 2, 3]

m = len(y) 

def cost_function(theta0,theta1):
	predicted_y = [theta0+(theta1*1), theta0+(theta1*2), theta0+(theta1*3)]
	sum=0
	for i,j in zip(predicted_y,y):
		sum = sum+((i-j)**2) 
	J = 1/(2*m)*sum 
	return (J)
	
theta0 = [1.5,0,1]
theta1 = [0,1.5,0.5]

for i,j in zip(theta0,theta1):
	print ("cost when theta0=%r theta1=%r :"%(i,j), cost_function(i,j))