base (version 3.2.0)

character: Character Vectors

Description

Create or test for objects of type "character".

Usage

character(length = 0)
as.character(x, ...)
is.character(x)

Arguments

length

A non-negative integer specifying the desired length. Double values will be coerced to integer: supplying an argument of length other than one is an error.

x

object to be coerced or tested.

...

further arguments passed to or from other methods.

Value

character creates a character vector of the specified length. The elements of the vector are all equal to "".as.character attempts to coerce its argument to character type; like as.vector it strips attributes including names. For lists and pairlists (including language objects such as calls) it deparses the elements individually, except that it extracts the first element of length-one character vectors.is.character returns TRUE or FALSE depending on whether its argument is of character type or not.

Details

as.character and is.character are generic: you can write methods to handle specific classes of objects, see InternalMethods. Further, for as.character the default method calls as.vector, so dispatch is first on methods for as.character and then for methods for as.vector.

as.character represents real and complex numbers to 15 significant digits (technically the compiler's setting of the ISO C constant DBL_DIG, which will be 15 on machines supporting IEC60559 arithmetic according to the C99 standard). This ensures that all the digits in the result will be reliable (and not the result of representation error), but does mean that conversion to character and back to numeric may change the number. If you want to convert numbers to character with the maximum possible precision, use format.

References

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

See Also

paste, substr and strsplit for character concatenation and splitting, chartr for character translation and casefolding (e.g., upper to lower case) and sub, grep etc for string matching and substitutions. Note that help.search(keyword = "character") gives even more links.

deparse, which is normally preferable to as.character for language objects.

Examples

form <- y ~ a + b + c
as.character(form)  ## length 3
deparse(form)       ## like the input

a0 <- 11/999          # has a repeating decimal representation
(a1 <- as.character(a0))
format(a0, digits = 16) # shows one more digit
a2 <- as.numeric(a1)
a2 - a0               # normally around -1e-17
as.character(a2)      # normally different from a1
print(c(a0, a2), digits = 16)