Implementation of the pass index technique for examination of open-field phase precession. Support for place cells, grid cells, and any dimentionality included. Plotting methods included up to three dimensions (3D). If used or modified, we would appreciate it if you cited our paper: Climer, J. R., Newman, E. L. and Hasselmo, M. E. (2013), Phase coding by grid cells in unconstrained environments: two-dimensional phase precession. European Journal of Neuroscience, 38: 2526–2541. doi: 10.1111/ejn.12256