小编Kam*_*mil的帖子

给出如下列表:

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按照指定的顺序使用以下操作对特定月份(例如1月或1月)的值(即内部列表的第二项)求和:

1. groupBy
2. slice
3. collect
4. sum