Basics of cluster analysis

Cluster Analysis in Python

Shaumik Daityari

Business Analyst

What is a cluster?

A group of items with similar characteristics
Google News: articles where similar words and word associations appear together
Customer Segments

Clustering algorithms

Hierarchical clustering
K means clustering
Other clustering algorithms: DBSCAN, Gaussian Methods

Hierarchical clustering in SciPy

from scipy.cluster.hierarchy import linkage, fcluster
from matplotlib import pyplot as plt
import seaborn as sns, pandas as pd

x_coordinates = [80.1, 93.1, 86.6, 98.5, 86.4, 9.5, 15.2, 3.4, 
                 10.4, 20.3, 44.2, 56.8, 49.2, 62.5, 44.0]
y_coordinates = [87.2, 96.1, 95.6, 92.4, 92.4, 57.7, 49.4, 
                 47.3, 59.1, 55.5, 25.6, 2.1, 10.9, 24.1, 10.3]

df = pd.DataFrame({'x_coordinate': x_coordinates,
                   'y_coordinate': y_coordinates})

Z = linkage(df, 'ward')
df['cluster_labels'] = fcluster(Z, 3, criterion='maxclust')

sns.scatterplot(x='x_coordinate', y='y_coordinate', 
                hue='cluster_labels', data = df)
plt.show()

K-means clustering in SciPy

from scipy.cluster.vq import kmeans, vq
from matplotlib import pyplot as plt
import seaborn as sns, pandas as pd

import random
random.seed((1000,2000))

x_coordinates = [80.1, 93.1, 86.6, 98.5, 86.4, 9.5, 15.2, 3.4, 
                 10.4, 20.3, 44.2, 56.8, 49.2, 62.5, 44.0]
y_coordinates = [87.2, 96.1, 95.6, 92.4, 92.4, 57.7, 49.4, 
                 47.3, 59.1, 55.5, 25.6, 2.1, 10.9, 24.1, 10.3]

df = pd.DataFrame({'x_coordinate': x_coordinates, 'y_coordinate': y_coordinates})

centroids,_ = kmeans(df, 3)
df['cluster_labels'], _ = vq(df, centroids)

sns.scatterplot(x='x_coordinate', y='y_coordinate', 
                hue='cluster_labels', data = df)
plt.show()

Next up: hands-on exercises

Cluster Analysis in Python