>> x <- factor(1:3, labels = c("b" , "f", "minus")) >> x > [1] b f minus > Levels: b f minus > > I want to change all "minus" to "b". I know that the simplest way to do this > is > >> levels(x) <- c("b", "f", "b") > > and also that > >> x[x == "minus"] <- "b" >> x <- factor(x) > > works. But why not > >> x <- ifelse(x == "minus", "b", x) >> x <- factor(x) > x > [1] 1 2 b > Levels: 1 2 b >
I find particulary usefull the list approach. Here is the example from levels help page. I like this approach, since you can modify list and apply it to a factor via levels. ## we can add levels this way: f <- factor(c("a","b")) levels(f) <- c("c", "a", "b") f f <- factor(c("a","b")) levels(f) <- list(C="C", A="a", B="b") f I was playing around this last week and wrote a simple function[1], which can save you some work in getting such a list from a factor. Is R core interested in it? [1]http://www.bfro.uni-lj.si/MR/ggorjan/software/R/ggmisc/factorMap.R -- Lep pozdrav / With regards, Gregor Gorjanc ---------------------------------------------------------------------- University of Ljubljana PhD student Biotechnical Faculty Zootechnical Department URI: http://www.bfro.uni-lj.si/MR/ggorjan Groblje 3 mail: gregor.gorjanc <at> bfro.uni-lj.si SI-1230 Domzale tel: +386 (0)1 72 17 861 Slovenia, Europe fax: +386 (0)1 72 17 888 ---------------------------------------------------------------------- "One must learn by doing the thing; for though you think you know it, you have no certainty until you try." Sophocles ~ 450 B.C. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel