> * Sam Steingold <[email protected]> [2012-02-13 16:14:36 -0500]: > > suppose I have two factor vectors: > x <- as.factor(c("a","b","a","c","b","c")) > y <- as.factor(c("b","a","a","c","c","b")) > I can compute their entropies: > entropy(table(x)) > [1] 1.098612 > using > library(entropy) > but it is not clear how to compute their mutual information directly. > I can compute the joint entropy as > entropy(table(paste(x,y,sep="")))
this can be simplified to entropy(table(x,y)) > [1] 1.791759 > and then mutual information will be h(x) + h(y) - h(x,y) = > 1.098612 + 1.098612 - 1.791759 > 0.405465 > > but I was wondering whether there was a better way (without creating a > fresh factor vector and a fresh factor class, both of which are > immediately discarded). -- Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X 11.0.11004000 http://www.childpsy.net/ http://ffii.org http://mideasttruth.com http://thereligionofpeace.com http://americancensorship.org http://memri.org If money were measured in piles, I would have had a pit of it. ______________________________________________ [email protected] 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.
