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

make.names

### 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 4.2.0 Index]