linear regression with 1 variable in python

gistfile1.py

testset = [
    [1, 4],
    [2, 8],
    [3, 12],
    [4, 16]
]

theta0 = 0
theta1 = 0
learningrate = 0.01

# h of theta(x) = theta0 + theta1 * x
def hypo(something):
    global theta0
    global theta1

    return theta0 + (theta1 * something)

def ms1(testset):
    s = 0
    for element in testset:
        s = s + (hypo(element[0]) - element[1])

    return 1.0/len(testset) * s

def ms2(testset):
    s = 0
    for element in testset:
        s = s + ((hypo(element[0]) - element[1]) * element[0])

    return 1.0/len(testset) * s

def compute(testset):
    global theta0
    global theta1

    print "Starting with theta0 = %s" % theta0
    print "Starting with theta1 = %s" % theta1

    prev = [0, 0]
    while(True):
        new_theta0 = theta0 - (learningrate * ms1(testset))
        new_theta1 = theta1 - (learningrate * ms2(testset))

        theta0 = new_theta0
        theta1 = new_theta1

        #print "%s - %s" % (theta0, theta1)

        if theta0 == prev[0] and theta1 == prev[1]:
            return prev

        prev = [theta0, theta1]


compute(testset)

assert round(hypo(5)) == 20.0
assert round(hypo(20)) == 80.0