Make Character Strings Unique

make.unique {base}

R Documentation

Make Character Strings Unique

Description

Makes the elements of a character vector unique by appending sequence numbers to duplicates.

Usage

make.unique(names, sep = ".")

Arguments

`names`	a character vector
`sep`	a character string used to separate a duplicate name from its sequence number.

Details

The algorithm used by make.unique has the property that make.unique(c(A, B)) == make.unique(c(make.unique(A), B)).

In other words, you can append one string at a time to a vector, making it unique each time, and get the same result as applying make.unique to all of the strings at once.

If character vector A is already unique, then make.unique(c(A, B)) preserves A.

Value

A character vector of same length as names with duplicates changed, in the current locale's encoding.

Author(s)

Thomas P. Minka

Examples

make.unique(c("a", "a", "a"))
make.unique(c(make.unique(c("a", "a")), "a"))

make.unique(c("a", "a", "a.2", "a"))
make.unique(c(make.unique(c("a", "a")), "a.2", "a"))

## Now show a bit where this is used :
trace(make.unique)
## Applied in data.frame() constructions:
(d1 <- data.frame(x = 1, x = 2, x = 3)) # direct
 d2 <- data.frame(data.frame(x = 1, x = 2), x = 3) # pairwise
stopifnot(identical(d1, d2),
          colnames(d1) == c("x", "x.1", "x.2"))
untrace(make.unique)

[Package base version 3.6.0 Index]