| levels {base} | R Documentation |
levels provides access to the levels attribute of a variable.
The first form returns the value of the levels of its argument
and the second sets the attribute.
The assignment form ("levels<-") of levels is a generic
function and new methods can be written for it.
The most important method is that for factors:
levels(x) levels(x) <- value
x |
an object, for example a factor. |
value |
A valid value for levels(x).
For the default method, NULL or a character vector. For the
factor method, a vector of character strings with length at
least the number of levels of x, or a named list specifying how to
rename the levels. |
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
## assign individual levels
x <- gl(2, 4, 8)
levels(x)[1] <- "low"
levels(x)[2] <- "high"
x
## or as a group
y <- gl(2, 4, 8)
levels(y) <- c("low", "high")
y
## combine some levels
z <- gl(3, 2, 12)
levels(z) <- c("A", "B", "A")
z
## same, using a named list
z <- gl(3, 2, 12)
levels(z) <- list(A=c(1,3), B=2)
z
## 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