Hi, I noticed whether some one could explain why "&" and "&&" behave differently in data frame transformations.
Consider the following : a<-data.frame(r=c(0,0,2,3),g=c(0,2,0,2.1)) Then: > transform(a,R=ifelse(r>0 && g> 0,log(r/g),NA)) r g R 1 0 0.0 NA 2 0 2.0 NA 3 2 0.0 NA 4 3 2.1 NA but > transform(a,R=ifelse(r>0 & g> 0,log(r/g),NA)) r g R 1 0 0.0 NA 2 0 2.0 NA 3 2 0.0 NA 4 3 2.1 0.3566749 If my understanding of the differences between "&" and "&&" and how 'transform' works are accurate, both statements should produce the same output. I got the same behaviour in Windows XP Pro 32-bit (running R v 2.7) and Ubuntu Hardy (running the same version of R). Thanks Christos Argyropoulos University of Pittsburgh Medical Center _________________________________________________________________ Discover the new Windows Vista E ______________________________________________ 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.
