Removing Duplicate Vector Elements in R

r
A note on using the make.unique() function to make duplicate vector elements unique.
Published

2026-01-27

Modified

2026-01-27

Note

Original Japanese version: Rでベクトルの重複を取り除く方法

Using the make.unique() Function

This is a note on how to handle duplicate elements in a vector in R and turn them into unique elements. With the make.unique() function, duplicate elements can be automatically converted into unique values by adding suffixes. The usage is as follows.

make.unique(names, sep = ".")
  • names: a character vector you want to make unique
  • sep: the separator used before the suffix added to duplicate elements; the default is a dot, .

Example

Suppose we have the following vector.

x <- c("apple", "banana", "apple", "orange", "banana")

Applying make.unique() to this vector gives the following result.

unique_x <- make.unique(x)
print(unique_x)
[1] "apple"    "banana"   "apple.1"  "orange"   "banana.1"

Because apple and banana are duplicated, .1 is added after the repeated words.

Closing Note

I cannot remember exactly where I used this function, but I remembered using it before and left this note. The opportunities to use it may be limited, but it can be useful to know.