These functions extract a designated subset of an object of class
`"fv"`

, or replace the designated subset with other data,
or delete the designated subset.

The subset is specified by the
row index `i`

and column index `j`

, or
by the column name `name`

. Either `i`

or `j`

may be missing, or both may be missing.

The function `[.fv`

is a method for the generic operator
`[`

for the class `"fv"`

. It extracts the
designated subset of `x`

, and returns it as
another object of class `"fv"`

(if `drop=FALSE`

)
or as a data frame or vector (if `drop=TRUE`

).

The function `[<-.fv`

is a method for the generic operator
`[<-`

for the class `"fv"`

.
If `value`

is `NULL`

, the designated subset of `x`

will be
deleted from `x`

.
Otherwise, the designated subset of `x`

will be
replaced by the data contained in `value`

.
The return value is the modified object `x`

.

The function `$<-.fv`

is a method for the generic operator
`$<-`

for the class `"fv"`

.
If `value`

is `NULL`

, the designated column of `x`

will be
deleted from `x`

.
Otherwise, the designated column of `x`

will be
replaced by the data contained in `value`

.
The return value is the modified object `x`

.