R: Combine Values into a Vector or List

c {base}

R Documentation

Combine Values into a Vector or List

Description

This is a generic function which combines its arguments.

The default method combines its arguments to form a vector. All arguments are coerced to a common type which is the type of the returned value, and all attributes except names are removed.

Usage

## S3 Generic function
c(...)

## Default S3 method:
c(..., recursive = FALSE, use.names = TRUE)

Arguments

...

objects to be concatenated. All NULL entries are dropped before method dispatch unless at the very beginning of the argument list.

recursive

logical. If recursive = TRUE, the function recursively descends through lists (and pairlists) combining all their elements into a vector.

use.names

logical indicating if names should be preserved.

Details

The output type is determined from the highest type of the components in the hierarchy NULL < raw < logical < integer < double < complex < character < list < expression. Pairlists are treated as lists, whereas non-vector components (such as names / symbols and calls) are treated as one-element lists which cannot be unlisted even if recursive = TRUE.

If the output type is complex, logical, integer, and double NAs keep their imaginary parts zero when coerced, and hence will not become NA_complex_ (with imaginary part NA).

There is a c.factor method which combines factors into a factor.

c is sometimes used for its side effect of removing attributes except names, for example to turn an array into a vector. as.vector is a more intuitive way to do this, but also drops names. Note that c methods other than the default are not required to remove attributes (and they will almost certainly preserve a class attribute).

This is a primitive function.

Value

NULL or an expression or a vector of an appropriate mode. (With no arguments the value is NULL.)

S4 methods

This function is S4 generic, but with argument list (x, ...).

References

⁠Becker RA, Chambers JM, Wilks AR (1988). The New S Language. Chapman and Hall/CRC, London.

Examples

c(1, 7:9)
c(1:5, 10.5, "next")

## uses with a single argument to drop attributes
x <- 1:4
names(x) <- letters[1:4]
x
c(x)          # has names
as.vector(x)  # no names
dim(x) <- c(2,2)
x
c(x)
as.vector(x)

## append to a list:
ll <- list(A = 1, c = "C")
## do *not* use
c(ll, d = 1:3) # which is == c(ll, as.list(c(d = 1:3)))
## but rather
c(ll, d = list(1:3))  # c() combining two lists

## descend through lists:
c(list(A = c(B = 1)), recursive = TRUE)
c(list(A = c(B = 1, C = 2), B = c(E = 7)), recursive = TRUE)

[Package base version 4.6.0 Index]