## Import libraries

import numpy as np
import random
import matplotlib.pyplot as plt


## Data

X = [*range(1, 51)]
Y = list(map(lambda x: 2*x + 5, X))


## Univariate Regression

$h(\theta) = \theta*X + b$

### MSE cost function

$\sum (h(x) - y)^2$


repeat {

Ø = Ø - ∆J(Ø) = Ø - LR*1/m * sum((h(Ø, b) - Y)*X)

b = b - ∆J(b) =  b - LR*1/m * sum((h(Ø, b) - Y))
}
def mse(y_true, y_pred):
cost = 0
m = len(y_pred)
for i in range(m):
cost += (y_pred[i] - y_true[i]) ** 2
return cost/(2*m)

def der_mse(y_true, y_pred):
der_cost = 0
m = len(y_pred)
for i in range(m):
der_cost += (y_pred[i] - y_true[i])
return der_cost

def predict(x):
return w*x + b

# Intialization of variables

m = len(X)
LR = 0.01
w,b =0,0.1

epochs = 10000
# Training

total_cost = []
for i in range(epochs):
y_pred = []
epoch_cost = []
for num, data in enumerate(zip(X, Y)):
x, y = data
y_pred = []
y_pred.append(w*x + b)

cost = mse(Y[num:num+1], y_pred)
epoch_cost.append(cost)
der_cost = der_mse(Y[num:num+1], y_pred)

w -= LR * (1/m) * der_cost * x
b -= LR * (1/m) * der_cost

total_cost.append(np.mean(epoch_cost))
if i%500==0:
print(f'epoch:{i}\t\tcost:{cost}')

epoch:0		cost:0.024546020195931887
epoch:500		cost:0.0035238913511105277
epoch:1000		cost:0.0004771777468473895
epoch:1500		cost:6.461567040474519e-05
epoch:2000		cost:8.749747634800157e-06
epoch:2500		cost:1.1848222450189964e-06
epoch:3000		cost:1.604393419109384e-07
epoch:3500		cost:2.1725438173628743e-08
epoch:4000		cost:2.9418885555175706e-09
epoch:4500		cost:3.983674896607656e-10
epoch:5000		cost:5.3943803161575866e-11
epoch:5500		cost:7.30464704919418e-12
epoch:6000		cost:9.891380608202818e-13
epoch:6500		cost:1.3394131683086816e-13
epoch:7000		cost:1.8137281109430194e-14
epoch:7500		cost:2.4560089530711338e-15
epoch:8000		cost:3.3257381016463754e-16
epoch:8500		cost:4.5034718706313674e-17
epoch:9000		cost:6.09814092196085e-18
epoch:9500		cost:8.25761584212193e-19

predict(2), predict(9)

(8.999999990490096, 22.999999991911498)
w, b

(2.000000000203057, 4.999999990083981)
plt.plot(total_cost)
plt.show()