c
Combine Values into a Vector or List
Description
Concatenates objects into a vector or a list.
The result is an atomic list if all of the objects are atomic;
otherwise, the result is a list.
Usage
c(..., recursive = FALSE)
## S3 method for class 'Date':
c(..., recursive = FALSE)
## S3 method for class 'POSIXct':
c(..., recursive = FALSE)
## S3 method for class 'POSIXlt':
c(..., recursive = FALSE)
## S3 method for class 'factor':
c(..., recursive = TRUE)
Arguments
| ... |
any objects. Missing values (NAs) are allowed.
The names of arguments become part of the names of the
resulting vector.
|
| recursive |
a logical value. If TRUE, indicates that the combining
should be done recursively, going up into lists.
The default is FALSE, but methods, such as c.factor, can override this.
|
Details
Arguments that are NULL or length 0 do not contribute
elements to the result.
Note that
c(...,recursive=TRUE) is equivalent to
unlist(list(...), recursive=TRUE).
The default method for the
c function also supports specifying a
use.names argument, with default value
TRUE. This
argument is interpreted similar to the
use.names of
unlist. It is not displayed in the argument list above,
because it is not present in the S3/S4 generics for 'c'.
c.factor was introduced in TERR-6.0. Prior to that, combining
factors with c gave an integer vector that was the concatenation
of the integer codes of the factor arguments.
Value
returns a vector or a list that is the combination of all values
from all arguments to the function. If recursive is
TRUE, arguments with recursive modes are effectively
unlisted (see unlist) before they are used.
The mode of the result is the most general of all the modes in the
arguments (or the unlisted arguments, if recursive=TRUE).
In particular, list objects can be combined this way.
The names attribute of the result is generated
from the argument names, if any, plus the names of the
combined objects. See unlist for the rule used.
Attributes of objects that are bound with other objects are deleted.
The c.Date(), c.POSIXct(), and c.POSIXlt() return
combined date-time objects of their respective class type.
c.factor(), if all of its arguments are factors, returns
a factor whose levels attribute contains the union of the levels
attributes of its arguments. If all the arguments are ordered factors
with identical levels, then the outut is an ordered factor
with those levels.
See Also
Examples
c(1:10, 1:5, 1:10)
c(2, 3, 5, 7, 11, 13)
c(a=1, b=2) # vector with names "a" and "b"
c(Sdatasets::state.name, "Washington DC")
# a list of 4 numeric vectors
c(list(1:3, a=3:6), list(8:23, c(3, 8, 39)))
# a numeric vector of length 26
c(list(1:3, a=3:6), list(8:23, c(3, 8, 39)), recursive=TRUE)
# build x, element by element
# useful if final length not known in advance
## Not run:
x <- numeric(0)
for(i in possibles)
if(test(i)) x <- c(x, fun(i))
## End(Not run)
## combine date-time objects
c(Sys.Date() + 365, Sys.Date() + 2, as.Date("2009-12-12"))
c(Sys.time() + 365, Sys.time() + 2, as.POSIXct("2009-12-12 01:02:03"))
c(as.POSIXlt(Sys.time() + 365), as.POSIXlt(Sys.time() + 2),
as.POSIXlt("2009-12-12 01:02:03"))
## combine factors
c(factor("A", levels=c("C","B","A")), factor(c("C","D")))
## demonstrate the use.names argument
c(c(A=1,B=2),c(Z=3))
## returns c(A=1,B=2,Z=3)
c(c(A=1,B=2),c(Z=3),use.names=FALSE)
## returns c(1,2,3)