The X-Means web app computes the AIC from:
- \(N_d\) - number of data points
- \(N_f\) - number of free parameters \(= 3 * K * N_{var}\)
- SSD - sum squared difference from the respective means
We use the AICc correction for small numbers:
$$AICc = AIC + (\frac{2 N_f(N_f + 1)}{N_d - N_f - 1})$$