"["(x, i, j, ..., drop = FALSE)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
Extract 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).
TRUE the result is
coerced to the lowest possible dimension (see the examples). This
only works for extracting elements, not for the replacement. See
drop for further details.
Extract