Linear regression of my weight

li_reg.py

import numpy as np
import matplotlib.pyplot as plt


def plot_result(O):
    sample_size = 50
    linX = np.linspace(np.min(npdata[:,1]), np.max(npdata[:,1]), num=sample_size)
    testX = np.concatenate((np.ones((sample_size, 1)), linX.reshape((sample_size, 1))), axis=1)
    y = np.dot(testX, O)
    plt.plot(linX, y[:,0], 'r-')


def feature_scale(data):
    for i in range(len(data[0])):
        std = np.std(data[:,i])
        median = np.median(data[:,i])
        data[:,i] = (data[:,i] - median) / std


if __name__ == '__main__':
    data = file("/Users/itarato/Desktop/weight.csv", 'r')
    npdata = np.genfromtxt(data, delimiter=',', skip_header=1)
    feature_scale(npdata)

    m = len(npdata)
    Y = npdata[:, 0].reshape((m, 1))
    a = 0.01
    iteration = 10000

    plt.plot(npdata[:,1], npdata[:,0], 'b^')

    X = np.concatenate((np.ones((m, 1)), npdata[:, 1].reshape((m, 1))), axis=1)

    O = np.array([0, 1]).reshape((2,1))

    a_per_m = (a / m)
    for i in range(iteration):
        h = np.dot(X, O)
        diff = h - Y
        O = O - (np.sum(X * diff, axis=0) * a_per_m).reshape((2, 1))

    plot_result(O)
    print(O)
    plt.show()