utils.py

import numpy as np
import matplotlib.pyplot as plt

def load_data():
    X = np.load("data/ex7_X.npy")
    return X

def draw_line(p1, p2, style="-k", linewidth=1):
    plt.plot([p1[0], p2[0]], [p1[1], p2[1]], style, linewidth=linewidth)

def plot_data_points(X, idx):
    # plots data points in X, coloring them so that those with the same
    # index assignments in idx have the same color
    plt.scatter(X[:, 0], X[:, 1], c=idx)
    
def plot_progress_kMeans(X, centroids, previous_centroids, idx, K, i):
    # Plot the examples
    plot_data_points(X, idx)
    
    # Plot the centroids as black 'x's
    plt.scatter(centroids[:, 0], centroids[:, 1], marker='x', c='k', linewidths=3)
    
    # Plot history of the centroids with lines
    for j in range(centroids.shape[0]):
        draw_line(centroids[j, :], previous_centroids[j, :])
    
    plt.title("Iteration number %d" %i)