an object to which the function will be applied - usually
a
groupedData object or a
data.frame.
FUN
function to apply to the distinct sets of rows
of the data frame
object defined by the values of
groups.
OPTIONAL ARGUMENTS:
which
an optional character or positive integer vector specifying which
columns of
object should be used with
FUN. Defaults to all columns
in
object.
form
an optional one-sided formula that defines the groups.
When this formula is given the right-hand side is evaluated in
object, converted to a factor if necessary, and the unique
levels are used to define the groups. Defaults to
formula(object).
level
an optional positive integer giving the level of grouping
to be used in an object with multiple nested grouping levels.
Defaults to the highest or innermost level of grouping.
groups
an optional factor that will be used to split the
rows into groups. Defaults to
getGroups(object, form, level).
...
optional additional arguments to the summary function
FUN. Often it is helpful to specify
na.rm = TRUE.
VALUE:
Returns a data frame with as many rows as there are levels in the
groups
argument.
SEE ALSO:
EXAMPLES:
## Find number of non-missing "conc" observations for each Subject
gapply( Quinidine, FUN = function(x) sum(!is.na(x$conc)) )