Machine Learning Algorithms

Adjusted rand index

The adjusted rand index measures the similarity between the original class partitioning (Y) and the clustering. Bearing in mind the same notation adopted in the previous scores, we can define:

• a: The number of pairs of elements belonging to the same partition in the class set C and to the same partition in the clustering set K
• b: The number of pairs of elements belonging to different partitions in the class set C and to different partitions in the clustering set K

If we total number of samples in the dataset is n, the rand index is defined as:

The Corrected for Chance version is the adjusted rand index, defined as follows: ...