The HOF package provides functions for hierachical logistic regressions, extended to bimodal models and a bootstrap approach to guarantee model stability. Such hierarchical models are also known as HOF models (Huisman-Olff-Fresco 1993) and can be used e.g. to model species distribution along ecological gradients.
Florian Jansen and Jari Oksanen
The functions in the eHOF package contain tools to model Extended Huisman-Olff-Fresco-Models to bounded responses to any gradient. The gradients (x-values) are internally standardized to 0 to 1.
Binary as well as continous response values can be modelled.
Huisman, J., Olff, H. & Fresco, L.F.M. (1993). A hierarchical set of models for species response analysis. Journal of Vegetation Science 4, 37-46. Jansen F, Oksanen J (2013) How to model species responses along ecological gradients - Huisman-Olff-Fresco models revisited. Journal of Vegetation Science. doi:10.1111/jvs.12050