给定如下列表:
val dane = List(
("2011-01-04", -137.76),
("2011-01-04", 2376.45),
("2011-01-04", -1.70),
("2011-01-04", -1.70),
("2011-01-04", -1.00),
// ... skip a few ...
("2011-12-22", -178.02),
("2011-12-29", 1800.82),
("2011-12-23", -83.97),
("2011-12-24", -200.00),
("2011-12-24", -30.55),
("2011-12-30", 728.00)
)
我想01
按指定的顺序使用以下操作对特定月份(例如一月或)的值(即内部列表的第二项)求和:
groupBy
slice
collect
sum