1. A method for generating a reduced rank matrix approximation for information retrieval, comprising: forming a term-by-document matrix A, wherein the elements of the matrix A represent a plurality of terms within a plurality of documents, the documents related to a plurality of topics; performing a singular value decomposition of the matrix A to identify a plurality of actual singular values each having a corresponding singular vector; selecting a subset of the actual singular values based on singular values that correspond to at least one desired topic; and determining a set of singular vectors based on the selected singular values, wherein the singular vectors provide an index for use during information retrieval.