make.names
Make Character Strings into Legal Names

Description

Makes character strings into legal names.

Usage

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

Arguments

names a character vector.
unique a logical flag. TRUE if the resulting set of names should be unique; otherwise, FALSE (the default).
allow_ a logical flag. TRUE (the default) if the underscore character is allowed to appear in names. If FALSE, the underscore character is converted to a period, like other non-name characters.

Details

The algorithm does the following:
  1. Adds the character "X" to the beginning of any string that does not start with a letter or a period (".").
  2. Replaces each illegal character with ".".
  3. Changes any names that are reserved names (such as "for", "function", and so on to non-reserved names by adding "." to the end.
  4. If unique is TRUE, duplicate names are made unique by adding ".<number>" as required.
Value
returns a character vector, each element of which is syntactically a legal name (that is, made up of letters, numbers, and "."). A legal name must not begin with a number. If allow_ is TRUE, then the underscore character is also allowed to appear in a name.
Examples
make.names(c("abc","ab??","1abc", ""))
# [1] "abc"   "ab.."  "X1abc" "X"

make.names(rep("A",5))
# [1] "A" "A" "A" "A" "A"
make.names(rep("A",5), unique=TRUE)
# [1] "A"   "A.1" "A.2" "A.3" "A.4"

make.names(c(rep("A",5), "A.3"), unique=TRUE)
# [1] "A"   "A.1" "A.2" "A.4" "A.5" "A.3"
#  note that the fourth element becomes "A.4",
#  since "A.3" already exists

make.names(rep("",5), unique=TRUE)
# [1] "X"   "X.1" "X.2" "X.3" "X.4"

make.names(c("_A","A_","_"))
# [1] "X_A" "A_"  "X_"
make.names(c("_A","A_","_"), allow_=FALSE)
# [1] "X.A" "A."  "X."

make.names(c("for", "function"))
# [1] "for."      "function."
Package base version 6.1.1-7
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