Cluster Analysis with R: How to Group Similar Data Points

Cluster Analysis with R: How to Group Similar Data Points: Cluster analysis is a statistical technique used to group similar data points into clusters or segments. It is a useful tool in data analysis, especially when dealing with large datasets, to identify patterns and structure within the data. Cluster analysis can be applied to various fields, such as marketing, biology, and social sciences. In this article, we will explore how to perform cluster analysis using the R programming language.

Types of Clustering

There are two main types of clustering techniques, hierarchical and partitioning. Hierarchical clustering creates a tree-like structure that shows the relationship between data points, whereas partitioning clustering divides data into distinct clusters based on certain criteria. In this article, we will focus on the partitioning clustering technique, specifically k-means clustering.

Cluster Analysis with R How to Group Similar Data Points
Cluster Analysis with R How to Group Similar Data Points

K-Means Clustering

K-means clustering is a popular partitioning clustering technique used to group data points into K clusters. The K-means algorithm works by minimizing the sum of squared distances between each data point and the centroid of its cluster. The centroid is the center point of each cluster.

To perform k-means clustering in R, we first need to install and load the “stats” package. This package contains the “kmeans” function that we will use to cluster our data.


Next, we need to import our data into R. For this example, we will use the built-in “iris” dataset that contains measurements of three different species of iris flowers.


The “iris” dataset contains four numeric variables: Sepal. Length, Sepal.Width, Petal.Length, and Petal.Width. We will use these variables to cluster the iris flowers into K groups.

To perform k-means clustering on the iris dataset, we need to specify the number of clusters we want to create. In this example, we will create three clusters since there are three species of iris flowers in the dataset.

kmeans_result <- kmeans(iris[,1:4], centers = 3)

The “kmeans” function takes two arguments, the first argument is the dataset, and the second argument is the number of clusters we want to create. We also set the seed value to ensure that our results are reproducible.

We can access the results of our clustering analysis by calling the “kmeans_result” object. The “kmeans_result” object contains several components, including the cluster centers and the cluster assignments for each data point.


The “centers” component contains the centroid coordinates for each cluster, and the “cluster” component contains the cluster assignments for each data point.

To visualize our clustering results, we can use the “ggplot2” package to create a scatterplot of the iris dataset, colored by cluster assignment.


iris$cluster <- kmeans_result$cluster
ggplot(iris, aes(x=Petal.Length, y=Petal.Width, color=as.factor(cluster))) + geom_point()

The scatterplot shows the iris flowers grouped into three clusters based on their Petal.Length and Petal.Width measurements.

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