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

nchar {base} | R Documentation

## 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`.

`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

`x` | 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 <= 3.2.0.

### 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.

### 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.

### Note

This does not by default give the number of characters that will be used to `print()` the string. Use `encodeString` to find that. This is particularly important on Windows when \uxxxx sequences have been used to enter Unicode characters not representable in the current encoding. Thus `nchar("\u2642")` is `1`, and it is printed in `Rgui` as one character, but it will be printed in `Rterm` as `<U+2642>`, which is what `encodeString` gives.

The concept of ‘width’ is a slippery one even in a monospaced font. Some human languages have the concept of combining characters, in which two or more characters are rendered together: an example would be `"y\u306"`, which is two characters of width one: combining characters are given width zero, and there are other zero-width characters such as the zero-width space `"\u200b"`.

Some East Asian languages have ‘wide’ characters, ideographs which are conventionally printed across two columns when mixed with ASCII and other ‘narrow’ characters in those languages. The problem is that whether a computer prints wide characters over two or one columns depends on the font, with it not being uncommon to use two columns in a font intended for East Asian users and a single column in a ‘Western’ font. Unicode has encodings for ‘fullwidth’ versions of ASCII characters and ‘halfwidth’ versions of Katakana (Japanese) and Hangul (Korean) characters. Then there is the ‘East Asian Ambiguous class’ (Greek, Cyrillic, signs, some accented Latin chars, etc), for which the historical practice was to use two columns in East Asia and one elsewhere. The width quoted by `nchar` for characters in that class (and some others) depends on the locale, being one except in some East Asian locales on some OSes (notably Windows).

Control characters are given width zero.

### 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/

### See Also

`strwidth` giving width of strings for plotting; `paste`, `substr`, `strsplit`

### Examples

    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)

[Package base version 3.5.1 Index]