Hello, I have observed the following odd behavior of "is.na( )" and hope someone can give me an explanation Example: X1=rep(1:2,5)[-1] X2=rep(1:5,rep(2,5))[-1] y= runif(9) y[3]=NA xtabs(y~x1+x2)
Now xtabs(is.na(y)~x1+x2) says that cell 2,2 is NA x2 x1 1 2 1 0 0 2 0 1 3 0 0 4 0 0 5 0 0 Whereas xtabs(!is.na(y)~x1+x2) says that all but cell 1,1 and 2,2 are not NA x2 x1 1 2 1 0 1 2 1 0 3 1 1 4 1 1 5 1 1 An explanation will be much appriciated ______________________________________________ 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.
