This repository contains C code implementing an algorithm for approximating the empirical entropy of a data stream. The code is now unmaintained, but I am posting it here in the hope that it will be useful. The algorithm was originally described in the paper "A Near-Optimal Algorithm for Estimating the Entropy of a Stream" by Chakrabarti, Cormode, and McGregor (SODA 2007, TALG 2010). The implementation was developed in 2007 in conjunction with the Research Experience for Undergraduates at DIMACS (see http://dimax.rutgers.edu/~jthaler/).