Create a Program to Implement K Means Clustering in Python Assignment Solution
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- Instructions
- Requirements and Specifications
Instructions
Objective
Write a python assignment program to implement K means clustering.
Requirements and Specifications
Source Code
import numpy as np
from scipy.spatial.distance import cdist
import matplotlib.pyplot as plt
data = np.loadtxt('data_points.txt', delimiter=',')
data.shape
### Define number of clusters, tolerance and maximum number of iterations
K = 4
tol = 1E-6
max_iters = 15
### Pick centroids
centroids = data[np.random.choice(data.shape[0], K),:]
print(centroids)
### Begin with K-Means Clustering Algorithm
# Define a numpy array to label each point
labels = np.zeros((data.shape[0],1))
# Define initial error
err = 1E10
iters = 0
while err > tol and iters < max_iters:
# Calculate distances to centroids
distances = cdist(data, centroids)
# Pick the minimum distance index
idx = np.argmin(distances, axis = 1)
# Now, update centroids
old_centroids = centroids.copy()
for k in range(K):
# Calculate the new value of centroid k
idxs_ = np.where(idx == k)[0]
centroid = np.mean(data[idxs_], axis = 0)
centroids[k] = centroid
labels[idxs_] = k
# Now, compute error
err = np.max(np.abs(old_centroids - centroids))
iters = iters + 1
# Print
print("Iteration {0}, error = {1:.8f}".format(iters, err))
### Plot centroids and points
plt.figure()
for k in range(K):
idxs_ = np.where(labels == k)[0]
p = data[idxs_,:]
plt.scatter(p[:,0], p[:,1], label = f"K = {k}", marker="+")
# Plot centroids
plt.scatter(centroids[:,0], centroids[:,1], color='black', marker = "x")
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