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, or an object that can be coerced to character by as.character.
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.

Value

A character vector of the same length and with the same attributes as x (after possible coercion).

Elements of the result will be have the encoding declared as that of the current locale (see Encoding if the corresponding input had a declared encoding and the current locale is either Latin-1 or UTF-8. The result will be in the current locale's encoding unless the corresponding input was in UTF-8, when it will be in UTF-8 when the system has Unicode wide characters.

See Also

sub and gsub for other substitutions in strings.

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'

## -- Very simple insecure crypto --
rot <- function(ch, k = 13) {
   p0 <- function(...) paste(c(...), collapse="")
   A <- c(letters, LETTERS, " '")
   I <- seq_len(k); chartr(p0(A), p0(c(A[-I], A[I])), ch)
}

pw <- "my secret pass phrase"
(crypw <- rot(pw, 13)) #-> you can send this off

## now ``decrypt'' :
rot(crypw, 54 - 13)# -> the original:
stopifnot(identical(pw, rot(crypw, 54 - 13)))

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