Elbow method (clustering)

Explained variance. The "elbow" is indicated by the red circle. The number of clusters chosen should therefore be 4.

In cluster analysis, the elbow method is a heuristic used in determining the number of clusters in a data set. The method consists of plotting the explained variation as a function of the number of clusters and picking the elbow of the curve as the number of clusters to use. The same method can be used to choose the number of parameters in other data-driven models, such as the number of principal components to describe a data set.

The method can be traced to speculation by Robert L. Thorndike in 1953.[1]

  1. ^ Robert L. Thorndike (December 1953). "Who Belongs in the Family?". Psychometrika. 18 (4): 267–276. doi:10.1007/BF02289263. S2CID 120467216.