Cluster Analysis in R With Big Data Applications

Cluster Analysis in R With Big Data Applications

Alicia Taylor Lamere
DOI: 10.4018/979-8-3693-3026-5.ch022
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Abstract

This chapter discusses several popular clustering functions and open source software packages in R and their feasibility of use on larger datasets. These will include the kmeans() function, the pvclust package, and the DBSCAN (density-based spatial clustering of applications with noise) package, which implement K-means, hierarchical, and density-based clustering, respectively. Dimension reduction methods such as PCA (principle component analysis) and SVD (singular value decomposition), as well as the choice of distance measure, are explored as methods to improve the performance of hierarchical and model-based clustering methods on larger datasets. These methods are illustrated through an application to a dataset of RNA-sequencing expression data for cancer patients obtained from the Cancer Genome Atlas Kidney Clear Cell Carcinoma (TCGA-KIRC) data collection from The Cancer Imaging Archive (TCIA).
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Background

The basic concept behind all clustering methods is to group together similar datapoints based on the variables that describe them. Through this clustering, we can observe characteristics that distinguish data points from cluster to cluster, leading to potential hypotheses about our population. We can also use these clusters to identify subsets of our population, which we can focus on separately in future analysis. This clustering is generally accomplished by measuring the distance between these data points and grouping those that have the smallest distances between them. The goal is to maximize the separation between different clusters while minimizing the separation between data points within each cluster. An important consideration, then, becomes how we choose to measure this distance.

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