Write K-means from scratch
Created | |
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Tags | ML Coding |
class KMeans:
def __init__(self, n_clusters = 3, random_state = 0):
assert n_clusters >=1, "n_clusters must be valid"
self.n_clusters = n_clusters
self.random_state = random_state
np.random.seed(self.random_state)
def L2(self, M, N):
return np.sqrt(np.sum((M -N)**2, axis=1))
def get_label(self, center, X):
return np.array([np.argmin(self.L2(center, item)) for item in X])
def get_center(self, labels, X):
return np.array([np.mean(X[labels == i], axis= 0) for i in range(self.n_clusters)])
def fit_predict(self, X, n_iter = 10):
k = self.n_clusters
center_index = np.random.choice(X.shape[0], self.n_clusters, replace=False)
center = X[center_index]
n_iter = n_iter
while n_iter>0:
last_center = center
labels = self.get_label(last_center, X)
center = self.get_center(labels, X)
self.cluster_center = center
if np.allclose(last_center, center):
self.labels = self.get_label(center, X)
break
n_iter += 1
return self
yf implement
import numpy as np
import random
class KMeans:
def __init__(self, n_clusters = 3, random_state = 0):
assert n_clusters >= 1, "must be valid"
self._n_clusters = n_clusters
self._random_state = random_state
self._X = None
self.cluster_centers_ = None
def distance(self, M, N):
return (np.sum((M - N) ** 2, axis = 1))** 0.5
def _generate_labels(self, center, X):
return np.array([np.argmin(self.distance(center, item)) for item in X])
def _generate_centers(self, labels, X):
return np.array([np.average(X[labels == i], axis=0) for i in np.arange(self._n_clusters)])
def fit_predict(self, X):
k = self._n_clusters
if self._random_state:
random.seed(self._random_state)
center_index = np.random.choice(np.arange(X.shape[0]), size = k, replace = False)
center = X[center_index]
n_iters = 1e3
while n_iters > 0:
last_center = center
labels = self._generate_labels(last_center, X)
self.labels_ = labels
center = self._generate_centers(labels, X)
self.cluster_centers_ = center
if (last_center == center).all():
self.labels_ = self._generate_labels(center, X)
break
n_iters -= 1
return
import numpy as np
import matplotlib.pyplot as plt
from sklearn.datasets import load_iris
# test
t1 = np.linspace(-1, 1.5, 100)
t2 = np.linspace(-1, 1.5, 100)
X = np.array([(x, y) for x in t1 for y in t2])
print(f"X.shape={X.shape}") # (10000, 2)
plt.figure(figsize=(10, 10))
clf = KMeans(n_clusters=3, random_state=None)
clf.fit_predict(X)
plt.scatter(X[:, 0], X[:, 1], c=clf.labels_)
center = clf.cluster_centers_
plt.scatter(center[:, 0], center[:, 1],marker="*",s=200)
plt.show()
print('center=', clf.cluster_centers_)