R: Character Translation and Casefolding

chartr {base}

R Documentation

Character Translation and Casefolding

Description

Translate characters in character vectors, in particular from upper to lower case or vice versa.

Usage

chartr(old, new, x)
tolower(x)
toupper(x)
casefold(x, upper = FALSE)

Arguments

`x`	a character vector.
`old`	a character string specifying the characters to be translated.
`new`	a character string specifying the translations.
`upper`	logical: translate to upper or lower case?.

Details

chartr translates each character in x that is specified in old to the corresponding character specified in new. Ranges are supported in the specifications, but character classes and repeated characters are not. If old contains more characters than new, an error is signaled; if it contains fewer characters, the extra characters at the end of new are ignored.

tolower and toupper convert upper-case characters in a character vector to lower-case, or vice versa. Non-alphabetic characters are left unchanged.

casefold is a wrapper for tolower and toupper provided for compatibility with S-PLUS.

Examples

x <- "MiXeD cAsE 123"
chartr("iXs", "why", x)
chartr("a-cX", "D-Fw", x)
tolower(x)
toupper(x)

## "Mixed Case" Capitalizing - toupper( every first letter of a word ) :

.simpleCap <- function(x) {
  s <- strsplit(x, " ")[[1]]
  paste(toupper(substring(s, 1,1)), substring(s, 2), sep="", collapse=" ")
}
.simpleCap("the quick red fox jumps over the lazy brown dog")
## ->  [1] "The Quick Red Fox Jumps Over The Lazy Brown Dog"

## and the better, more sophisticated version:
capwords <- function(s, strict = FALSE) {
    cap <- function(s) paste(toupper(substring(s,1,1)),
                         {s <- substring(s,2); if(strict) tolower(s) else s},
                             sep = "", collapse = " " )
    sapply(strsplit(s, split = " "), cap, USE.NAMES = !is.null(names(s)))
}
capwords(c("using AIC for model selection"))
## ->  [1] "Using AIC For Model Selection"
capwords(c("using AIC", "for MODEL selection"), strict=TRUE)
## ->  [1] "Using Aic"  "For Model Selection"
##                ^^^        ^^^^^
##               'bad'       'good'