Matrix Factorization and Latent Semantic Indexing What it is From term-doc matrix A, we compute the approximation Ak There is a row for each term and a column for each doc in a k Thus docs live in a space of k<<r dimensions a These dimensions are not the original axes But whyMatrix Factorization and Latent Semantic Indexing 25 What it is ▪ From term-doc matrix A, we compute the approximation Ak. ▪ There is a row for each term and a column for each doc in Ak ▪ Thus docs live in a space of k<<r dimensions ▪ These dimensions are not the original axes ▪ But why? LSI