This article is about Data Science
Clustering Techniques for Data Science: An Overview
By NIIT Editorial
Published on 19/06/2023
Grouping data points that are similar into clusters or segments is a common unsupervised machine learning strategy in data science. Similarities and patterns within the data are discovered by the algorithm in this method without the requirement for manual labelling or categorization.
Knowing these phrases and ideas can help you grasp the notion of clustering. How far apart or alike two data points are may be determined by using the distance metric. Clustering algorithms are used to categorise data into groups with shared characteristics, and the number of clusters is the total number of groups into which the data will be divided.
Clustering plays a crucial role in data science because it enables researchers to unearth hidden links and patterns in information. Anomalies and outliers may be found, which helps with quality assurance and spotting fraud. Market segmentation, picture and pattern recognition, and recommendation systems are just a few of the many uses for clustering.
Table of Contents
- Types of Clustering
- Common Clustering Algorithms
- Evaluation Metrics for Clustering
- Applications of Clustering in Data Science
- Best Practices for Clustering
- Challenges and Limitations of Clustering
Types of Clustering
Clustering may be broken down into two distinct categories: hierarchical and partitioning.
As its name implies, hierarchical clustering builds a hierarchy of clusters. There are two distinct forms of this clustering: agglomerative and divisive. Divisive clustering begins with all data points in a single cluster and splits them into smaller clusters, while agglomerative clustering begins with individual data points and eventually merges them into bigger clusters. The algorithm in hierarchical clustering uses the data to determine how many clusters to create.
In contrast, the data points in partitioning clustering are separated into distinct groups. The user or algorithm chooses the number of clusters. The k-means technique is the most popular partitioning algorithm because it seeks to minimise the sum of squared distances (or eigenvectors) between data points and their assigned cluster centres. Fuzzy C-means and hierarchical divisive clustering are two other techniques for splitting data.
Clusters are formed differently in hierarchical and partitioned clustering. Clusters may be formed by either partitioning or hierarchical clustering, with the latter method producing non-overlapping groups.
Using similarities in traits like leaf size, petal length, etc., to group together diverse plant species is an example of hierarchical clustering. Once all plant species are in a single cluster or the target number of clusters is attained, the algorithm will combine the most related species to produce bigger clusters.
Clustering clients into subgroups according to their buying habits is an example of partitioning clustering. Based on their previous purchases, the algorithm classifies clients into a certain number of clusters, then places them in the group with the most similar average spending habits.
Both k-means and hierarchical clustering have their uses, and which one is best depends on the data and the task at hand.
Common Clustering Algorithms
Each of the various clustering methods out there has its own set of advantages and disadvantages. Three of the most popular clustering methods are as follows:
1. K-Means Clustering
K-means clustering is a clustering technique that seeks to split data in such a way as to minimise the sum of squared distances between each data point and the cluster centres. Each data point is first allocated to one of k randomly selected cluster centres, and then the algorithm repeatedly shifts the centre of each cluster to the average of the points it has been assigned. When there is no longer any appreciable movement at the cluster centres, the algorithm terminates.
- K-means requires little to no memory and can process massive datasets with ease.
- K-means may be effective if clusters are sufficiently distinct and of about the same size.
- K-means may converge to a poor solution depending on the original cluster centre selection.
- K-means does not perform well with clusters that have non-spherical or irregular shapes.
Example: K-means clustering may be used to divide clients into subsets delineated by their spending habits, allowing for more targeted advertising.
Density-Based Spatial Clustering of Applications in Noisy Environments is the abbreviation for DBSCAN. Closely related data points are clustered together and distinguished from other data points that do not belong to any cluster. Clusters are defined as zones of high density that are divided by lower density regions.
- DBSCAN is flexible enough to deal with clusters of any size or form.
- DBSCAN is indifferent to the settings with which it is first used.
- The accuracy of DBSCAN fluctuates depending on which distance measure and settings are used.
- Datasets with different densities may be problematic for DBSCAN.
Example: With DBSCAN, law enforcement organisations may more effectively deploy resources by pinpointing areas with a high concentration of reported crimes.
3. Hierarchical Clustering Algorithms
There are two distinct categories of hierarchical clustering algorithms: agglomerative and divisive. Divisive clustering begins with all data points in a single cluster and splits them into smaller clusters, while agglomerative clustering begins with individual data points and eventually merges them into bigger clusters.
- Different sized and shaped clusters provide no problem for hierarchical clustering.
- Through hierarchical clustering, you can see how the clusters are connected to one another.
- For big datasets, hierarchical clustering may be time-consuming and resource-intensive to compute.
- It's possible for noise and outliers to mess with hierarchical clustering's accuracy.
Example: Different patterns of gene expression in a microarray experiment set may be identified via hierarchical clustering, which can then be utilised by biologists to locate possible biomarkers for the diagnosis and treatment of illness.
The data and the task at hand dictate which of these methods should be used, each having advantages and disadvantages.
Evaluation Metrics for Clustering
Metrics for evaluation play an essential role in determining the efficacy of clustering algorithms. They provide a numerical evaluation of how well various clustering algorithms can divide information into discrete groups.
The most popular measures of clustering performance are:
1. Silhouette Coefficient
When compared to objects in other clusters, this metric indicates how closely they resemble those in their own cluster. It may take on values between -1 and 1, with higher scores suggesting more effective grouping.
2. Davies-Bouldin Index
The average degree of similarity between two clusters is calculated using this metric. A smaller number suggests more accurate grouping.
3. Calinski-Harabasz Index
The inter-cluster variance-to-intra-cluster variance ratio is the focus of this statistic. A greater value suggests more accurate grouping.
Each measure has its own unique way of assessing similarity inside clusters and dissimilarity across clusters in order to evaluate the quality of clustering.
The average silhouette coefficient is determined, for instance, by using the silhouette coefficient on all of the data. A data point's silhouette coefficient is determined by averaging the distances between that data point and all other data points in the same cluster (a) and the closest cluster (b) (b). The data point's silhouette coefficient is then determined using the formula (b-a)/max (a,b).
In practise, these measures may be used to assess how well various clustering approaches work, and to fine-tune the settings of a single approach to provide the best possible results.
Applications of Clustering in Data Science
Cluster analysis has many practical uses in many fields. Cluster analysis has several popular uses in the field of data science, including the following:
1. Customer Segmentation
Customers that have similar qualities and behaviours may be grouped together using clustering for more effective consumer segmentation. This allows companies to better target certain demographics of customers and provide individualised experiences. Clustering may be used in many different contexts; for instance, a business might use it to categorise consumers according to their demographics, purchasing habits, and past purchases.
2. Fraud Detection
In order to spot suspicious patterns or behaviours, cluster analysis is often employed in the anti-fraud industry. For the purpose of identifying suspicious trends or outliers, a bank may utilise clustering to categorise credit card transactions by factors such as geographical location, transaction value, and time of day.
3. Image Segmentation
In image segmentation, clustering is used to collect pixels that are visually similar and then extract those clusters from the rest of the picture. This is useful in a variety of contexts, including object identification and computer vision. Clustering may be used to divide a tumour picture into various sections, which can then be utilised to better diagnose and treat the disease.
4. Anomaly Detection
Anomaly detection makes use of clustering to find data points or events that don't fit a predefined pattern. As a result, problems may be spotted before they become serious. Cluster analysis may help a factory find the faulty equipment that's causing all the problems in the production line.
Best Practices for Clustering
Best practises, which must be adhered to for clustering to be effective, include:
1. Choosing the Right Algorithm:
Picking a clustering technique that works for your data collection and your issue is crucial. Knowing the benefits and drawbacks of each algorithm will help you choose wisely.
2. Preprocessing Data:
The data must be preprocessed so that the clustering algorithm can read and understand it. Some examples of this include eliminating outliers, standardising data, and dealing with missing numbers.
Selecting Appropriate Evaluation Metrics:
For a reliable assessment of the clustering outcomes, using the right evaluation measure is essential. It is vital to understand the features of the data and the issue being addressed in order to choose the appropriate measure from the wide variety of assessment tools available.
Adhering to these guidelines can help you get more reliable clustering results and deeper insights into your data.
Challenges and Limitations of Clustering
Although very useful, clustering is not without its caveats in the field of data science. While dealing with clustering, you could encounter problems like:
1. Choosing the Right Number of Clusters:
Finding the right number of clusters to divide a dataset into is not always easy.
2. Handling High-Dimensional Data:
The "curse of dimensionality," in which the distance between data points loses all significance after being clustered, is a potential outcome of working with high-dimensional data.
3. Dealing with Noise and Outliers:
Noise and outliers may degrade the quality of clusters when using a clustering technique.
4. Interpreting the Results:
As an unsupervised learning method, the meaning or interpretation of the generated clusters may be arbitrary.
Some of the limitations of clustering include:
- Subjectivity: Each analyst has their own preferences when it comes to the optimal clustering technique, cluster size, and measures for success.
- Sensitivity to Initialization: Different iterations of a clustering algorithm may provide wildly diverse outcomes due to their sensitivity to their beginning circumstances.
- Scalability: It is possible that large-scale implementations of certain clustering techniques are computationally prohibitive.
It is suggested that in order to overcome these obstacles and constraints,
- Preprocess the Data: Feature selection, normalisation, and dimensionality reduction are all preprocessing approaches that may improve clustering by reducing noise and outliers.
- Experiment With Different Algorithms and Parameters: It is crucial to experiment with various clustering methods and settings and to assess their effectiveness using suitable metrics.
- Visualize the Results: The conclusions and underlying patterns in the data may be better understood by a visual representation of the clusters.
- Combine Clustering with Other Techniques: Using clustering with additional methods like classification, regression, and association rule mining may improve the efficiency and clarity of the results.
Clustering may be an effective method for revealing previously unseen patterns and insights in data, provided that certain best practices are adhered to and the obstacles and limits are surmounted.
This article provided an overview of clustering in data science, covering its different flavours (hierarchical and partitioning), popular algorithms (k-means, DBSCAN, and hierarchical), evaluation metrics (silhouette coefficient, Davies-Bouldin index, and Calinski-Harabasz index), practical applications (customer segmentation, fraud detection, image segmentation, and anomaly detection), and recommended procedures for getting the job done right. The paper went on to describe methods for addressing clustering's drawbacks.
Understanding the many facets of the clustering approach is critical for its effective use in data science. Accurate and efficient clustering may be achieved by adhering to best practises and taking into account the obstacles and restrictions.
We recommend enrolling in a data science course if you're interested in learning more about data science and clustering.