TITLE(Extract @@ Extract or Replace Parts of an Object)
USAGE(
x[i]
x[i,j, ...]
x[i,j, ... , drop=TRUE]
x[[i]]
x[[i,j, ...]]
x$name
)
ALIAS(Extract)
ALIAS(Subscript)
ALIAS([)
ALIAS([[)
ALIAS($)
DESCRIPTION(
These operators act on vectors, matrices, dataframes and lists.
If one of these expressions is on the left hand side of an assignment
then that part of LANG(x) is set to the value of the right hand side
of the assignment.
PARA
These operators are generic. You can write methods to handle subsetting
of specific classes of data.
PARA
The LANG([[) operator requires all relavent subscripts be supplied.
With  the LANG([) operator a comma separated blank indicates that all
entries in that dimension are selected.
PARA
When operating on a list the  LANG([[) operator gives the specified
element of the list while the LANG([) operator returns a list with
the specified element(s) in it.
)
SEEALSO(
LANG(LINK(list)), LANG(LINK(array)), LANG(LINK(matrix)).
)
EXAMPLES(
x <- 1:12; m <- matrix(1:6,nr=2); li <- list(pi=pi, e = exp(1))
x[10]   # the tenth element of x
m[1,]   # the first row of matrix m
m[1, , drop = FALSE]# is a 1-row matrix
li[[1]] # the first element of list li
y<-list(1,2,a=4,5)
y[c(3,4)] # a list containing the third and fourth elements of y
y$a      #the element of y named a
)
KEYWORD(array)
KEYWORD(list)
