rank {base}R Documentation

Sample Ranks

Description

Returns the sample ranks of the values in a vector. Ties, i.e., equal values, result in ranks being averaged, by default.

Usage

rank(x, na.last = TRUE,
     ties.method = c("average", "first", "random", "max", "min"))

Arguments

x a numeric, complex, character or logical vector.
na.last for controlling the treatment of NAs. If TRUE, missing values in the data are put last; if FALSE, they are put first; if NA, they are removed; if "keep" they are kept.
ties.method a character string specifying how ties are treated, see below; can be abbreviated.

Details

If all components are different, the ranks are well defined, with values in 1:n where n <- length(x) and we assume no NAs for the moment. Otherwise, with some values equal, called ‘ties’, the argument ties.method determines the result at the corresponding indices. The "first" method results in a permutation with increasing values at each index set of ties. The "random" method puts these in random order whereas the default, "average", replaces them by their mean, and "max" and "min" replaces them by their maximum and minimum respectively, the latter being the typical “sports” ranking.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

order and sort.

Examples

(r1 <- rank(x1 <- c(3, 1, 4, 15, 92)))
x2 <- c(3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5)
names(x2) <- letters[1:11]
(r2 <- rank(x2)) # ties are averaged

## rank() is "idempotent": rank(rank(x)) == rank(x) :
stopifnot(rank(r1) == r1, rank(r2) == r2)

## ranks without averaging
rank(x2, ties.method= "first")  # first occurrence wins
rank(x2, ties.method= "random") # ties broken at random
rank(x2, ties.method= "random") # and again

## keep ties ties, no average
(rma <- rank(x2, ties.method= "max"))  # as used classically
(rmi <- rank(x2, ties.method= "min"))  # as in Sports
stopifnot(rma + rmi == round(r2 + r2))

[Package base version 2.1.0 Index]