unlist
Simplify the Structure of a List
Description
Returns a vector or a list that is the result of simplifying the
recursive structure of the input list.
Usage
unlist(x, recursive = TRUE, use.names = TRUE)
Arguments
| x |
a vector. Typically a list.
|
| recursive |
a logical value. If TRUE (the default), the unlisting should be
done recursively.
|
| use.names |
a logical value. If TRUE (the default), the function uses the rule
described in the Details section to construct a names
attribute for the result.
If FALSE, the resulting object does not have a names attribute.
|
Details
If
use.names is
TRUE, names are built from the component
names according to the following rules:
- If i is a component of x, and iname
represents its corresponding name, then, in the unlisted version,
i has names that are made by pasting iname and the
names attribute of i, with separator "."
(assuming that both strings are non-empty).
- If iname is the empty string (that is, i has no
component name) just the names attribute of i is used,
if it exists.
- If iname is not empty, but i has no names
attribute, then iname is used, followed by the index of the
corresponding element in i. (It has no separating "." in
this case, and if i has length 1, the redundant "1" is
not added.)
- If recursive is TRUE, the rule above is applied,
bottom up, recursively. The same rule applies to names created by the
c() function, with the equivalence shown below.
The algorithm does not enforce rules on the names, such as uniqueness or
that every name be non-empty. Use names(x) <- make.names(names(x),
unique=TRUE) to enforce such rules.
- c(..., recursive=TRUE) is equivalent to
unlist(list(...), recursive=TRUE).
Value
returns a vector or list created by combining the components of
x.
(See Help for the
c function for more information on combining
components.)
- If x is atomic or an expression, x is returned unmodified.
- If x is a list of factors, the factors are combined into one.
- If recursive is TRUE, each component of x is
unlisted (with recursive=TRUE) before it is combined.
Using the idea of
x as a tree, calling
unlist with
recursive=TRUE produces a vector of all the leaves.
The mode of the result is the most general of all the modes of the
components of
x, or of the leaves of
x if
recursive
is
TRUE.
See Also
Examples
lista <- list(1:3, a=5:7, b=list(b1=12:14, b2=c(23, 25, 28)))
unlist(lista) # a vector of length 12
unlist(lista, recursive=F)
# a list of length 8 with final components b.b1 and b.b2
# equivalent to list(1, 2, 3, a1=5, a2=6, a3=7,
# b.b1=12:14, b.b2=c(23,25,28))
x <- list(A=1,B=c(a=2,b=3,4),list(d=5,6)) # names construction
unlist(x)
# A B.a B.b B3 d
# 1 2 3 4 5 6