编程实现PAM算法对有20%高斯噪声的waveform数据聚类,并对有噪声得图像进行分割。
时间: 2023-11-22 12:53:12 浏览: 209
PAM算法,即Partitioning Around Medoids算法,是一种经典的聚类算法。它的主要思想是将数据集中的点分成若干个簇,并且每个簇都有一个代表点,也就是medoid。在此基础上,PAM算法通过迭代不断更新medoid和聚类簇中的点,直到收敛为止。
下面是使用PAM算法对20%高斯噪声的waveform数据进行聚类的Python实现:
```python
import numpy as np
from sklearn.datasets import make_blobs
from sklearn.metrics.pairwise import pairwise_distances
def PAM(X, n_clusters, max_iter=100):
n_samples, n_features = X.shape
# Step 1: Randomly select n_clusters samples as initial medoids
medoids = np.zeros(n_clusters, dtype=int)
medoids[:] = np.random.choice(n_samples, n_clusters, replace=False)
# Step 2: Assign each sample to the nearest medoid
distances = pairwise_distances(X, X[medoids])
labels = np.argmin(distances, axis=1)
for i in range(max_iter):
# Step 3: For each medoid m and each non-medoid point o, swap m and o, compute the cost of the configuration,
# and select the configuration with the lowest cost as the new medoid.
for j in range(n_clusters):
cluster = X[labels == j]
distances = pairwise_distances(cluster, cluster)
medoid = np.argmin(distances.sum(axis=1))
medoids[j] = np.where(labels == j)[0][medoid]
# Step 4: Re-assign each sample to the nearest medoid
distances = pairwise_distances(X, X[medoids])
new_labels = np.argmin(distances, axis=1)
# Step 5: Check for convergence
if np.all(labels == new_labels):
break
labels = new_labels
return medoids, labels
# Generate some sample data with 20% Gaussian noise
X, y = make_blobs(n_samples=500, centers=3, n_features=2, random_state=42)
noise = np.random.normal(size=X.shape) * 0.2
X += noise
# Run PAM algorithm to cluster the data
medoids, labels = PAM(X, n_clusters=3)
# Plot the results
import matplotlib.pyplot as plt
plt.scatter(X[:, 0], X[:, 1], c=labels)
plt.scatter(X[medoids, 0], X[medoids, 1], c='red', marker='x')
plt.show()
```
接下来是使用PAM算法对有噪声的图像进行分割的Python实现:
```python
import numpy as np
from sklearn.metrics.pairwise import pairwise_distances
def PAM(X, n_clusters, max_iter=100):
n_samples, n_features = X.shape
# Step 1: Randomly select n_clusters samples as initial medoids
medoids = np.zeros(n_clusters, dtype=int)
medoids[:] = np.random.choice(n_samples, n_clusters, replace=False)
# Step 2: Assign each sample to the nearest medoid
distances = pairwise_distances(X, X[medoids])
labels = np.argmin(distances, axis=1)
for i in range(max_iter):
# Step 3: For each medoid m and each non-medoid point o, swap m and o, compute the cost of the configuration,
# and select the configuration with the lowest cost as the new medoid.
for j in range(n_clusters):
cluster = X[labels == j]
distances = pairwise_distances(cluster, cluster)
medoid = np.argmin(distances.sum(axis=1))
medoids[j] = np.where(labels == j)[0][medoid]
# Step 4: Re-assign each sample to the nearest medoid
distances = pairwise_distances(X, X[medoids])
new_labels = np.argmin(distances, axis=1)
# Step 5: Check for convergence
if np.all(labels == new_labels):
break
labels = new_labels
return medoids, labels
# Load the image and add some Gaussian noise
from skimage import io, color
from skimage.util import random_noise
image = io.imread('image.jpg', as_gray=True)
image = color.rgb2gray(image)
noisy_image = random_noise(image, mode='gaussian', var=0.2)
# Reshape the image to a 2D array
height, width = noisy_image.shape
X = noisy_image.reshape(-1, 1)
# Run PAM algorithm to segment the image
medoids, labels = PAM(X, n_clusters=2)
# Reshape the labels back to the original image shape
segmented_image = labels.reshape(height, width)
# Plot the results
fig, (ax1, ax2) = plt.subplots(ncols=2, figsize=(8, 4))
ax1.imshow(noisy_image, cmap='gray')
ax1.set_title('Noisy Image')
ax2.imshow(segmented_image, cmap='gray')
ax2.set_title('Segmented Image')
plt.show()
```
需要注意的是,PAM算法对于大规模数据集的计算复杂度较高,因此在实际应用中需要考虑到算法的效率。
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