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

A = 1.
B = 0.5
sigma = 0.3
xmax = 4.
numberOfClassEl = 200
data = []
sumx =0
sumg = 0
sumxg =0
sumxx =0
for rowNum in range(numberOfClassEl):
    X = random.random()*xmax
    sumx = sumx + X
    G = A+B*X+random.gauss(0,sigma)
    sumg = sumg + G
    sumxg = X*G + sumxg
    sumxx = X*X + sumxx
    data.append([X, G])

b = (sumxg/200 - sumx/200*sumg/200)/(sumxx/200 - (sumx/200)**2)
a = -b*sumx/200 + sumx/200
print(a, b)

f = np.linspace(0, 4, 200)
pl.plot(f, a+b*f)

pl.scatter([data[i][0] for i in range(len(data))],[data[i][1] for i in range(len(data))],)
pl.savefig('genLRdata.png')