Ok, if you mean to group "nba" together like
nba (3)
espn (1)
then you need to keep data like
var data = [
[1, 'Celtics', "nba", "nba.com/celtics:::nba", 339938.0, 36130.0],
[2, 'Blazers', "espn", "espn.com:::espn" , 315654.0, 11231.0],
[3, 'Pistons',"nba", "nba.com/pistons:::nba" , 9954.0, 11231.0],
[2, 'Raptors', "nba", "nba.com/raptors:::nba" , 9954.0, 11231.0]
];
keep the 4th column hidden and use values from 4th column in the renderer of 3rd column.