library(sparkR)
xx=as.DataFrame(sqlContext, data = mtcars)

head(agg(groupBy(xx, "gear", "cyl"), hp = 'max'))
  gear cyl max(hp)
1    3   8     **245**
2    5   4     113
3    3   4      97
4    4   4     109
5    5   6     175
6    3   6     110

head(agg(groupBy(xx, "gear", "cyl"), disp = 'max'))
  gear cyl max(disp)
1    3   8     472.0
2    5   4     120.3
3    3   4     120.1
4    4   4     146.7
5    5   6     145.0
6    3   6     258.0