Try this: t1 <- prop.table(table(factor(c(0,0,2,4,4), levels = 0:4))) t2 <- prop.table(table(factor(c(0,2,2,2,3), levels = 0:4)))
On Mon, Jul 27, 2009 at 4:21 PM, Andre Nathan <an...@digirati.com.br> wrote: > 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. > -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O [[alternative HTML version deleted]]
______________________________________________ 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.
