A package for identifying regions bound by transcription factors from aligned reads. PICS identifies binding event locations by modeling local concentrations of directional reads, and uses DNA fragment length prior information to discriminate closely adjacent binding events via a Bayesian hierarchical t-mixture model. It uses precalculated, whole-genome read mappability profiles and a truncated t-distribution to adjust binding event models for reads that are missing due to local genome repetitiveness. PICS estimates uncertainties in model parameters that can be used to define confidence regions on binding event locations and to filter estimates. Finally, it calculates a per-event enrichment score relative to a control sample, and can use a control sample to estimate a false discovery rate. Because it is based on mixture models and accounts for missing reads, PICS is computationally intensive.