We apply a recently proposed method for estimating generating partitions [Phys. Rev. E 70 (2004) 016215] to data of the chaotic response observed in a squid giant axon. Using the estimated partitions we argue that given the data, a binary symbol sequence of "firing" and "non-firing" leads to a complete description of the dynamics. (c) 2005 Elsevier B.V. All rights reserved.