base (version 3.5.0)

make.names: Make Syntactically Valid Names


Make syntactically valid names out of character vectors.


make.names(names, unique = FALSE, allow_ = TRUE)



character vector to be coerced to syntactically valid names. This is coerced to character if necessary.


logical; if TRUE, the resulting elements are unique. This may be desired for, e.g., column names.


logical. For compatibility with R prior to 1.9.0.


A character vector of same length as names with each changed to a syntactically valid name, in the current locale's encoding.


Some OSes, notably FreeBSD, report extremely incorrect information about which characters are alphabetic in some locales (typically, all multi-byte locales including UTF-8 locales). However, R provides substitutes on Windows, macOS and AIX.


A syntactically valid name consists of letters, numbers and the dot or underline characters and starts with a letter or the dot not followed by a number. Names such as ".2way" are not valid, and neither are the reserved words.

The definition of a letter depends on the current locale, but only ASCII digits are considered to be digits.

The character "X" is prepended if necessary. All invalid characters are translated to ".". A missing value is translated to "NA". Names which match R keywords have a dot appended to them. Duplicated values are altered by make.unique.

See Also

make.unique, names, character, data.frame.


Run this code
make.names(c("a and b", "a-and-b"), unique = TRUE)
# "a.and.b"  "a.and.b.1"
make.names(c("a and b", "a_and_b"), unique = TRUE)
# "a.and.b"  "a_and_b"
make.names(c("a and b", "a_and_b"), unique = TRUE, allow_ = FALSE)
# "a.and.b"  "a.and.b.1"
make.names(c("", "X"), unique = TRUE)
# "X.1" "X" currently; R up to 3.0.2 gave "X" "X.1"[make.names( !=] # those 10 with a space
# }

Run the code above in your browser using DataLab