When adding several logical vectors I expect each vector will be coerced to integers and these vectors will then be added.
That doesn't always seem to be the case. For example: > ( f1 <- as.factor ( sample ( "x" , 25 , rep = T ) ) ) [1] x x x x x x x x x x x x x x x x x x x x x x x x x Levels: x > ( f2 <- as.factor ( sample ( "y" , 25 , rep = T ) ) ) [1] y y y y y y y y y y y y y y y y y y y y y y y y y Levels: y > ( f3 <- as.factor ( sample ( "z" , 25 , rep = T ) ) ) [1] z z z z z z z z z z z z z z z z z z z z z z z z z Levels: z > > is.na ( f1 [ sample ( 1:25 , 4 ) ] ) <- + is.na ( f2 [ sample ( 1:25 , 4 ) ] ) <- + is.na ( f3 [ sample ( 1:25 , 4 ) ] ) <- TRUE > > ## this returns a numeric vector: > > is.na ( f1 ) + is.na ( f2 ) + is.na ( f3 ) [1] 0 0 0 0 0 1 1 0 0 0 1 0 0 1 0 0 1 0 1 2 2 0 1 0 1 > > ## but this returns a logical vector > > !is.na ( f1 ) + !is.na ( f2 ) + !is.na ( f3 ) [1] TRUE TRUE TRUE TRUE TRUE TRUE FALSE TRUE [9] TRUE TRUE TRUE TRUE TRUE FALSE TRUE TRUE [17] FALSE TRUE FALSE TRUE FALSE TRUE FALSE TRUE [25] FALSE > Can someone please explain why the returned value is a logical vector when I use the not operator but a numeric vector when I don't. What is special about the !is.na? it returns an object of class logical just like the is.na function: > all.equal ( class ( !is.na ( f1 ) ) , class ( is.na ( f1 ) ) ) [1] TRUE > Thanks! ______________________________________________ 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.
