Aggregate function: returns the last value in a group.
column to compute on.
further arguments to be passed to or from other methods.
a logical value indicating whether NA values should be stripped before the computation proceeds.
The function by default returns the last values it sees. It will return the last non-missing value it sees when na.rm is set to true. If all values are missing, then NA is returned. Note: the function is non-deterministic because its results depends on the order of the rows which may be non-deterministic after a shuffle.