这是我的第一个Dataframe：

val sample_df = Seq(("john","morning",1.5,0.0),("john","night",0.0,3.9),("bill","morning",0.4,0.0),("bill","night",0.0,2.3)).toDF("name","time_of_day","morning_min","night_min")

我想添加一个名为“row\u min”的列，如果行“time\u of \u day”是“morning”，则该列取“morning\u min”列的值，否则为“night\u min”列。
下面是生成的Dataframe的外观：

val resulting_df = Seq(("john","morning",1.5,0.0,1.5),("john","night",0.0,3.9,3.9),("bill","morning",0.4,0.0,0.4),("bill","night",0.0,2.3,2.3)).toDF("name","time_of_day","morning_min","night_min","row_min")

任何帮助都将不胜感激。祝你今天愉快。