nchar: Count the Number of Characters (or Bytes or Width)

Description

nchar takes a character vector as an argument and returns a vector whose elements contain the sizes of the corresponding elements of x. Internally, it is a generic, for which methods can be defined.

nzchar is a fast way to find out if elements of a character vector are non-empty strings.

Usage

nchar(x, type = "chars", allowNA = FALSE, keepNA = NA)
nzchar(x, keepNA = FALSE)

Arguments

character vector, or a vector to be coerced to a character vector. Giving a factor is an error.

type

character string: partial matching to one of c("bytes", "chars", "width"). See ‘Details’.

allowNA

logical: should NA be returned for invalid multibyte strings or "bytes"-encoded strings (rather than throwing an error)?

keepNA

logical: should NA be returned where ever x is NA? If false, nchar() returns 2, as that is the number of printing characters used when strings are written to output, and nzchar() is TRUE. The default for nchar(), NA, means to use keepNA = TRUE unless type is "width". Used to be (implicitly) hard coded to FALSE in R versions \(\le\) 3.2.0.

Value

For nchar, an integer vector giving the sizes of each element. For missing values (i.e., NA, i.e., NA_character_), nchar() returns NA_integer_ if keepNA is true, and 2, the number of printing characters, if false.

type = "width" gives (an approximation to) the number of columns used in printing each element in a terminal font, taking into account double-width, zero-width and ‘composing’ characters.

If allowNA = TRUE and an element is detected as invalid in a multi-byte character set such as UTF-8, its number of characters and the width will be NA. Otherwise the number of characters will be non-negative, so !is.na(nchar(x, "chars", TRUE)) is a test of validity.

A character string marked with "bytes" encoding (see Encoding) has a number of bytes, but neither a known number of characters nor a width, so the latter two types are NA if allowNA = TRUE, otherwise an error.

Names, dims and dimnames are copied from the input.

For nzchar, a logical vector of the same length as x, true if and only if the element has non-zero length; if the element is NA, nzchar() is true when keepNA is false, as by default, and NA otherwise.

Details

The ‘size’ of a character string can be measured in one of three ways (corresponding to the type argument):

bytes: The number of bytes needed to store the string (plus in C a final terminator which is not counted).
chars: The number of human-readable characters.
width: The number of columns cat will use to print the string in a monospaced font. The same as chars if this cannot be calculated.

These will often be the same, and almost always will be in single-byte locales (but note how type determines the default for keepNA). There will be differences between the first two with multibyte character sequences, e.g.in UTF-8 locales.

The internal equivalent of the default method of as.character is performed on x (so there is no method dispatch). If you want to operate on non-vector objects passing them through deparse first will be required.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Unicode Standard Annex #11: East Asian Width. http://www.unicode.org/reports/tr11/

Examples

Run this code

# NOT RUN {
x <- c("asfef", "qwerty", "yuiop[", "b", "stuff.blah.yech")
nchar(x)
# 5  6  6  1 15

nchar(deparse(mean))
# 18 17  <-- unless mean differs from base::mean

x[3] <- NA; x
nchar(x, keepNA= TRUE) #  5  6 NA  1 15
nchar(x, keepNA=FALSE) #  5  6  2  1 15
stopifnot(identical(nchar(x     ), nchar(x, keepNA= TRUE)),
          identical(nchar(x, "w"), nchar(x, keepNA=FALSE)),
          identical(is.na(x), is.na(nchar(x))))

##' nchar() for all three types :
nchars <- function(x, ...)
   vapply(c("chars", "bytes", "width"),
          function(tp) nchar(x, tp, ...), integer(length(x)))

nchars("\u200b") # in R versions (>= 2015-09-xx):
## chars bytes width
##     1     3     0

data.frame(x, nchars(x)) ## all three types : same unless for NA
## force the same by forcing 'keepNA':
(ncT <- nchars(x, keepNA = TRUE)) ## .... NA NA NA ....
(ncF <- nchars(x, keepNA = FALSE))## ....  2  2  2 ....
stopifnot(apply(ncT, 1, function(.) length(unique(.))) == 1,
          apply(ncF, 1, function(.) length(unique(.))) == 1)
# }

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