# make.unique

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##### Make Character Strings Unique

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

Keywords
character
##### 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.

make.names
library(base) # NOT RUN { 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) # }