import numpy as np
import math

def calculate_regressionCoeff(A, B):
# theta = (A_t @ A)^(-1) @ A_t @ b
res1 = (A.T@A)
res2 = np.linalg.inv(res1)@ A.T
print(res2)
res = res2 @ B
return res

A = np.array([
[1,1,1],
[1,2,3],
[1,3,4],
[1,4,3]
])

B = np.array([
[1],
[3],
[4],
[5]
])

res = calculate_regressionCoeff(A, B)
print(res)

R = A @ res - B #R laf sai so,
val_R = math.sqrt(R.T@R)
print(val_R)