Posted in Web text mining – How to calculate perplexity of a holdout with Latent … January 19, 2025 Perplexity is seen as a good measure of performance for LDA. The idea is that you keep a holdout sample, train your LDA on the rest of the data, then calculate the perplexity of the holdout. The perplexity could be given by the formula: https://stats.stackexchange.com/questions/18167/how-to-calculate-perplexity-of-a-holdout-with-latent-dirichlet-allocation