Apply an arbitrary permutation to the ordering of levels within a factor
permuteLevels(x, perm, ordered = is.ordered(x), invert = FALSE)The factor to be permuted
A vector specifying the permutation
Should the output be an ordered factor?
Use the inverse of perm to specify the permutation
Returns a factor with identical values, but with the ordering of the factor levels shuffled.
This is a convenience function used to shuffle the order in
which the levels of a factor are specified. It is similar in spirit to
the relevel function, but more general. The relevel
function only changes the first level of the factor, whereas
permuteLevels can apply an arbitrary permutation. This can be
useful for plotting data, because some plotting functions will display
the factor levels in the same order that they appear within the factor.
The perm argument is a vector of the same length as levels(x),
such that perm[k] is an integer that indicates which of the old
levels should be moved to position k. However, if invert=TRUE, the
inverse permutation is applied: that is, perm[k] is an integer
specifying where to move the k-th level of the original factor. See the
examples for more details.
# original factor specifies the levels in order: a,b,c,d,e,f
x <- factor( c(1,4,2,2,3,3,5,5,6,6), labels=letters[1:6] )
print(x)
#> [1] a d b b c c e e f f
#> Levels: a b c d e f
# apply permutation (5 3 2 1 4 6)... i.e., move 5th factor level (e)
# into position 1, move 3rd factor level (c) into position 2, etc
permuteLevels(x,perm = c(5,3,2,1,4,6))
#> [1] a d b b c c e e f f
#> Levels: e c b a d f
# apply the inverse of permutation (5 3 2 1 4 6)... i.e., move 1st
# level (a) into position 5, move 2nd level (b) into position 3, etc
permuteLevels(x,perm = c(5,3,2,1,4,6),invert=TRUE)
#> [1] a d b b c c e e f f
#> Levels: d c b e a f