A few packages which employ variations of generalized linear models (pscl and VGAM), specifically the functions hurdle(), zeroinfl() and vglm(). When a model formula is rank deficient, these functions give an error message. I'm guessing this happens for other modelling packages - any ideas for a general workaround for this type of problem?
Definitely have to thank all the package maintainers for the listed packages - I hope this doesn't come across as complaining! I'm also aware of this question, trying to think a general code-based approach.
