Hello I'm trying to write a function to calculate the relative entropy between two distributions. The data I have is in table format, for example:
> t1 <- prop.table(table(c(0,0,2,4,4))) > t2 <- prop.table(table(c(0,2,2,2,3))) > t1 0 2 4 0.4 0.2 0.4 > t2 0 2 3 0.2 0.6 0.2 The relative entropy is given by H[P||Q] = sum(p * log2(p/q)) with the conventions that 0*log2(0/q) = 0 and p*log2(p/0) = Inf. I'm not sure about what is the best way to achieve that. Is there a way to test if a table has a value for a given level, so that I can detect that, for example, t1 is missing levels 1 and 3 and t2 is missing levels 1 and 4 (is "level" the correct terminology here?)? Simply trying to access t1[["1"]], for example, gives a "subscript out of bounds" error. Another option would be to "expand" the tables, so that, for example, t1 becomes 0 1 2 3 4 0.4 0.0 0.2 0.0 0.4 Is there a way to do that? Thanks, Andre ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
