Collapsing levels of a factor
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
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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
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"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.