Determining the number of clusters

Elbow Methods

WCSS is the sum of squared distance between each point and the centroid in a cluster (i.e. cost function):

W C S S = \sum_{C l u s t e r j} \sum_{P o i n t_{i} i n C l u s t e r j} d i s t a n c e (P_{i}, C_{j})^{2}