"["(x, i)
numeric
or character
vectors or empty (missing) or NULL
. Numeric
values are coerced to integer as by
as.integer
(and hence truncated towards
zero). Character vectors will be matched to the
names
of the object (or for
matrices/arrays, the dimnames
): see
Character indices below for further details. For [
-indexing only: i
, j
,
...
can be logical vectors, indicating
elements/slices to select. Such vectors are recycled if
necessary to match the corresponding extent. i
,
j
, ...
can also be negative integers,
indicating elements/slices to leave out of the selection.
When indexing arrays by [
a single argument
i
can be a matrix with as many columns as there
are dimensions of x
; the result is then a vector
with elements corresponding to the sets of indices in
each row of i
.
An index value of NULL
is treated as if it were
integer(0)
.