On Jan 9, 2010, at 12:18 PM, Grant Ingersoll wrote: >> >> For text, you can actually compute perplexity which measures how well >> cluster membership predicts what words are used. This is nice because you >> don't have to worry about the entropy of real valued numbers. > > Do you have a good ref. on perplexity and/or some R code (or other)?
In looking a little more at this (via http://en.wikipedia.org/wiki/Perplexity), it seems we may already have most of this, given o.a.m.math.stats.LogLikelihood has the entropy calculation and this is just b^entropy() right? Or am I misreading? -Grant
