data.txt

95,85
85,95
80,70
70,65
60,70

regress.py

points = []

with open("data.txt", 'r') as f:
    lines = f.readlines()
    for line in lines:
        line = line.rstrip('\n')
        points.append([int(x) for x in line.split(',')])
        
sum_x, mean_x, sum_y, mean_y = 0, 0, 0, 0
for point in points:
    sum_x += point[0]
    sum_y += point[1]

mean_x = sum_x / len(points)
mean_y = sum_y / len(points)

a = []
b = []
ab = []
for point in points:
    current_a = point[0] - mean_x
    current_b = point[1] - mean_y
    a.append(current_a)
    b.append(current_b)
    ab.append(current_a * current_b)

b1_num = 0
b1_den = 0
for i in range(len(points)):
    b1_num += a[i] * b[i]
    b1_den += a[i] ** 2

b1 = b1_num / b1_den
b0 = mean_y - (b1 * mean_x)

print(points)
for i in range(len(points)):
    points[i][1] = b1 * points[i][0] + b0

print(b0, b1)
print(points)