What is Cluster Analysis in Data Mining? Methods, Benefits, and More
Updated on Jan 29, 2025 | 21 min read | 116.5k views
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Updated on Jan 29, 2025 | 21 min read | 116.5k views
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Large volumes of unlabeled data can make it challenging to pinpoint meaningful connections. Cluster analysis in data mining (Clustering) addresses this issue by grouping similar points together and highlighting patterns hidden in the mix.
This approach is often used for tasks like customer segmentation or market basket analysis since it reveals sets of related items without needing predefined labels.
In this blog, you’ll learn how clustering in data mining can simplify large-scale tasks by organizing data into manageable groups. You’ll also explore the core principles behind clustering, examine popular clustering methods in data mining, and discuss practical steps to prepare your data.
A cluster is a set of items that share certain features or behaviors. By grouping these items, you can spot patterns that might stay hidden if you treat each one separately. Cluster analysis in data mining builds on this idea by forming groups (clusters) without predefined labels.
It uses similarities between data points to highlight relationships that would be hard to see in a cluttered dataset, making it easier to understand massive datasets with no predefined labels.
Let’s take an example to understand this better:
Suppose you run an online learning platform. You collect data on thousands of learners:
By applying cluster analysis, you can form groups based on these study habits. You could design targeted course plans, streamline user experiences, and address specific learner needs in each group.
This helps you deliver focused support without sorting through heaps of data one record at a time.
As datasets grow, it becomes tough to see everything at once. Cluster analysis in data mining solves this by breaking down information into smaller, more uniform groups. This approach highlights connections that might remain hidden, supports decisions with data-driven insights, and saves time when you need to act on real trends.
Here are the key reasons why clustering in data mining is so important:
Also Read: Understanding Types of Data: Why is Data Important, its 4 Types, Job Prospects, and More
Clustering in data mining rests on certain ideas that shape how data points are gathered into meaningful groups. Each cluster aims to pull together points that share important traits while keeping dissimilar points apart. This may sound simple, but some nuances help you decide if your groups make sense.
When these aspects are handled well, cluster analysis results can guide decisions and uncover patterns you might otherwise miss.
Core Properties of Good Clusters
Here are the four properties that form the backbone of a strong clustering setup:
If these properties of clustering all hold together, your clusters stand a better chance of revealing trends you can trust.
When you set out to group data points, you have a range of well-known clustering methods in data mining at your disposal. Each one differs in how it draws boundaries and adapts to your dataset. Some methods split your data into a fixed number of groups, while others discover clusters based on density or probabilistic models.
Knowing these options will help you pick what fits your goals and the nature of your data.
The partitioning method divides data into non-overlapping clusters so that each data point belongs to only one cluster. It is suitable for datasets with clearly defined, separate clusters.
K-Means is a common example. It starts by choosing cluster centers and then refines them until each data point is close to its center. This method is quick to run but needs you to guess how many clusters work best.
Example:
Imagine you’re analyzing student attendance (in hours per week) and test scores (percentage) to see if there are two clear groups. You want to check if some students form a group that needs more help while others seem to be doing fine.
Here, k-means tries to form exactly two clusters.
import numpy as np
from sklearn.cluster import KMeans
# [attendance_hours_per_week, test_score_percentage]
X = np.array([
[3, 40], [4, 45], [2, 38],
[10, 85], [11, 80], [9, 90]
])
kmeans = KMeans(n_clusters=2, random_state=0)
kmeans.fit(X)
print("Cluster Centers:", kmeans.cluster_centers_)
print("Labels:", kmeans.labels_)
A hierarchical algorithm builds clusters in layers. One approach starts with each data point on its own, merging them step by step until everything forms one large group. Another starts with a single group and keeps splitting it.
You end up with a tree-like view, which shows how clusters connect or differ at various scales. It’s easy to visualize but can slow down with very large datasets.
Example:
You might record daily study hours and daily online forum interactions for a set of learners. You’re curious if a natural layering or grouping emerges, such as one big group that subdivides into smaller clusters.
import numpy as np
from sklearn.cluster import AgglomerativeClustering
# [study_hours, forum_interactions_per_day]
X = np.array([
[1, 2], [1, 3], [2, 2],
[5, 10], [6, 9], [5, 11]
])
agglo = AgglomerativeClustering(n_clusters=2, linkage='ward')
labels = agglo.fit_predict(X)
print("Labels:", labels)
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Also Read: Understanding the Concept of Hierarchical Clustering in Data Analysis: Functions, Types & Steps
The density-based method allows you to identify clusters as dense regions in data, effectively handling noise and outliers. Clusters are formed where data points are closely packed together, separated by areas of lower data density. It can be effectively used for irregularly shaped clusters and noisy data.
DBSCAN is a well-known example. It places points together if they pack closely, labeling scattered points as outliers. You don’t need to pick a cluster number, but you do set parameters that define density. This method captures odd-shaped groups and handles noisy data well.
Example:
Suppose you track weekly code submissions and average accuracy. Some learners cluster around moderate submission counts, while a few show very high accuracy with fewer submissions.
import numpy as np
from sklearn.cluster import DBSCAN
# [weekly_submissions, average_accuracy_percentage]
X = np.array([
[3, 50], [4, 55], [5, 60],
[10, 85], [11, 87], [9, 83],
[20, 95] # might be an outlier or a separate cluster
])
dbscan = DBSCAN(eps=3, min_samples=2)
labels = dbscan.fit_predict(X)
print("Labels:", labels)
Here, you divide the data space into cells, like squares on a grid. Then, you check how dense each cell is, merging those that touch and share similar density. By focusing on the cells instead of every single point, this method can work quickly on very large datasets.
It’s often chosen for spatial data or cases where you want a broad view of how points cluster together.
Example:
Here, the code maps each point to a cell. Each cell is two units wide. Once cells fill up with enough points, they could be merged if they sit next to cells with similar densities. This script shows a simple idea of splitting the space into cells.
import numpy as np
X = np.array([
[1, 2], [1, 3], [2, 2],
[8, 7], [8, 8], [7, 8],
[3, 2], [4, 2]
])
grid_size = 2
cells = {}
# Assign points to cells based on integer division
for x_val, y_val in X:
x_cell = int(x_val // grid_size)
y_cell = int(y_val // grid_size)
cells.setdefault((x_cell, y_cell), []).append((x_val, y_val))
clusters = []
for cell, points in cells.items():
clusters.append(points)
print("Grid Cells:", cells)
print("Total Clusters (basic grouping):", len(clusters))
In model-based clustering in data mining, you assume data follows certain statistical patterns, such as Gaussian distributions. The algorithm estimates these distributions and assigns points to the model that fits best.
This works well when you believe your data naturally falls into groups of known shapes, though it might struggle if the real patterns differ from those assumptions.
Example:
This snippet fits two Gaussian distributions to the data. It then assigns each point to whichever distribution provides the best fit. You see the mean of each distribution and how each point is labeled.
import numpy as np
from sklearn.mixture import GaussianMixture
X = np.array([
[1, 2], [2, 2], [1, 3],
[8, 7], [8, 8], [7, 7]
])
gmm = GaussianMixture(n_components=2, random_state=0)
gmm.fit(X)
labels = gmm.predict(X)
print("Means:", gmm.means_)
print("Labels:", labels)
Also Read: Gaussian Naive Bayes: Understanding the Algorithm and Its Classifier Applications
If you have rules that define how clusters must form, constraint-based methods let you apply them. These rules might involve distances, capacity limits, or domain-specific criteria. This approach gives you more control over the final groups, though it can be tricky if your constraints are too strict or your data doesn’t follow simple rules.
Example:
Say you run an online test series for a small group. You want no cluster to have fewer than three learners because otherwise, that group isn't very informative. This snippet modifies K-Means to respect a minimum size.
import numpy as np
from sklearn.cluster import KMeans
def constrained_kmeans(data, k, min_size=3, max_iter=5):
model = KMeans(n_clusters=k, random_state=0)
for _ in range(max_iter):
labels = model.fit_predict(data)
counts = np.bincount(labels)
if all(count >= min_size for count in counts):
return labels, model.cluster_centers_
for idx, size in enumerate(counts):
if size < min_size:
# Move this center so that cluster tries again
model.cluster_centers_[idx] = np.random.uniform(
np.min(data, axis=0),
np.max(data, axis=0)
)
return labels, model.cluster_centers_
X = np.array([
[2, 2], [1, 2], [2, 1],
[6, 8], [7, 9], [5, 7],
[2, 3]
])
labels, centers = constrained_kmeans(X, k=2)
print("Labels:", labels)
print("Centers:", centers)
Most clustering methods make a point belonging to exactly one cluster. Fuzzy clustering, on the other hand, allows a point to belong to several clusters with different levels of membership.
This is useful when data points share features across groups or when you suspect strict boundaries don’t capture the full story. You can fine-tune how strongly a point belongs to each group, which can give you a more nuanced understanding of overlapping patterns.
Example:
A set of learners might rely partly on recorded lectures and partly on live sessions. Instead of forcing them into a single group, you assign them to both with different strengths.
!pip install fcmeans # Install once in your environment
import numpy as np
from fcmeans import FCM
# [hours_recorded_lectures, hours_live_sessions]
X = np.array([
[2, 0.5], [2, 1], [3, 1.5],
[8, 3], [7, 2.5], [9, 4]
])
fcm = FCM(n_clusters=2)
fcm.fit(X)
labels = fcm.predict(X)
membership = fcm.u
print("Labels:", labels)
print("Membership Degrees:\n", membership)
A well-prepared dataset lays the groundwork for useful results. If your data has too many missing values or relies on mismatched scales, your clustering model could group points for the wrong reasons.
By focusing on good data hygiene — removing bad entries, choosing the right features, and keeping everything on a fair scale — you give your algorithm a reliable starting point. This way, any patterns you find are more likely to reflect actual relationships instead of noise or inconsistent units.
Key Steps to Get Your Data Ready
Following these steps puts you on firmer ground. Instead of grappling with disorganized data, your clusters emerge from well-structured information. This boosts the odds that your final insights will be accurate and meaningful.
Cluster analysis in data mining can simplify how you interpret large piles of data. Instead of trying to assess every point on its own, you group similar items so that any patterns or outliers become easier to notice. This saves you from manual sorting and makes many follow-up tasks, like predicting trends or identifying unusual behavior, much more straightforward.
Here are the key benefits of clustering:
Although clustering in data mining helps you uncover hidden patterns, there are times when it doesn’t fit the problem or the data. It’s good to know where these approaches struggle, so you can adjust your strategy or test different methods that offer better results for certain tasks.
Here are the key limitations of clustering you should know:
Clustering in data mining shines in areas where you handle diverse data and need to group items that share common traits. Whether you’re segmenting customers for focused marketing or spotting sudden shifts in large networks, this method finds natural patterns in the data.
Below is a snapshot of how different sectors put clustering into action.
Sector |
Application |
Retail & E-commerce |
|
Banking & Finance |
|
Healthcare |
|
Marketing & Advertising |
|
Telecommunications |
|
Social Media |
|
Manufacturing |
|
Education & EdTech |
|
IT & Software |
|
Once you build clusters, you must check if they represent meaningful groups. Validation helps confirm that your chosen method hasn’t formed accidental patterns or ignored important details.
Below are the main ways to measure your clusters' performance and suggestions for using these insights in practice.
Judging Cluster Performance Through Internal Validation
Internal methods rely only on the data and the clustering itself. They judge how cohesive each cluster is and whether different clusters stand apart clearly.
Here are the most relevant methods:
Transitioning to external checks is important when you have labels or extra information that you can compare against these internally formed clusters.
Judging Cluster Performance Through External Validation
Here, you compare your clusters to existing labels or categories in the data. External methods – listed below – measure how your unsupervised groups match up with known groupings.
Once you confirm your clusters match or explain real categories, you can apply the following practical steps to refine them further.
By monitoring these metrics and refining your method as needed, you end up with clusters that are easier to trust and explain.
Also Read: Data Cleaning Techniques: Learn Simple & Effective Ways To Clean Data
Picking a suitable clustering approach is key to getting reliable results. The method you use should match the size and shape of your data, along with the goals you have in mind.
Before you decide, weigh the following points:
Cluster analysis in data mining has come a long way, thanks to fresh ideas that tackle bigger datasets and more varied patterns. Researchers and data experts now try approaches that go beyond standard algorithms, drawing on concepts from deep learning, real-time data processing, and even specialized hardware.
These efforts aim to make clustering both faster and more adaptable to the problems you face.
For successful implementation of clustering in data mining, you need a solid knowledge of the various techniques and algorithms available and their applicability to specific types of data. upGrad offers you comprehensive learning opportunities to master these techniques and apply them effectively in real-world scenarios.
Here are some of upGrad’s courses related to data mining:
Need further help deciding which courses can help you excel in data mining? Contact upGrad for personalized counseling and valuable insights.
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