Question

我想创建一个data.table，其中包含巴士站之间的出发和到达时间。这是我data.table的格式。（下面可重复的数据集）

    trip_id stop_sequence arrival_time departure_time travel_time
 1:       a             1     07:00:00       07:00:00    00:00:00
 2:       a             2     00:00:00       00:00:00    00:02:41
 3:       a             3     00:00:00       00:00:00    00:01:36
 4:       a             4     00:00:00       00:00:00    00:02:39
 5:       a             5     00:00:00       00:00:00    00:02:28
 6:       b             1     07:00:00       07:00:00    00:00:00
 7:       b             2     00:00:00       00:00:00    00:00:00
 8:       b             3     00:00:00       00:00:00    00:01:36
 9:       b             4     00:00:00       00:00:00    00:00:37
10:       b             5     00:00:00       00:00:00    00:03:00

这是它应该如何工作的。这个想法是车辆按照停止顺序行驶。例如，在行程a中，车辆从00:02:41停靠1需要2。如果乘客在每个站点进入/离开车辆的固定时间为40秒，则公交车将在2

处离开"07:03:21"站。

这里的事情是这是两列之间的逐行迭代过程。直觉上，我会for set loop in data.table，但我无法理解这一点。帮助

可重现的数据集：

library(data.table)
library(chron)

dt <- structure(list(trip_id = c("a", "a", "a", "a", "a", "b", "b", 
      "b", "b", "b"), stop_sequence = c(1L, 2L, 3L, 4L, 5L, 1L, 2L, 
      3L, 4L, 5L), arrival_time = structure(c(0.291666666666667, 0, 
      0, 0, 0, 0.291666666666667, 0, 0, 0, 0), format = "h:m:s", class = "times"), 
      departure_time = structure(c(0.291666666666667, 0, 0, 0, 
      0, 0.291666666666667, 0, 0, 0, 0), format = "h:m:s", class = "times"), 
      travel_time = structure(c(0, 0.00186598685444013, 0.00110857958406301, 
      0.00183749407361369, 0.00171664297781446, 0, 0.000522388450578203, 
      0.00111473367541453, 0.000427755975518318, 0.00207918951573377
      ), format = "h:m:s", class = "times")), .Names = c("trip_id", 
      "stop_sequence", "arrival_time", "departure_time", "travel_time"
      ), class = c("data.table", "data.frame"), row.names = c(NA, -10L
      ))

预期输出前四行

   trip_id stop_sequence arrival_time departure_time travel_time
1:       a             1     07:00:00       07:00:00    00:00:00
2:       a             2     07:02:41       07:03:21    00:02:41
3:       a             3     07:04:57       07:05:37    00:01:36
4:       a             4     07:08:16       07:08:56    00:02:39

Answer 1

我认为没有循环就可以做到这一点。我认为您可以在没有循环的情况下计算departure_time，然后一旦有了，arrival_time只是departure_time - 40 seconds：

dt2 <- copy(dt)
dt2[,c("arrival_time", "departure_time") := .(cumsum(arrival_time + ifelse(travel_time==0, 0, travel_time + times("00:00:40"))) - ifelse(travel_time == 0 , 0, times("00:00:40")),
                                              cumsum(arrival_time + ifelse(travel_time==0, 0, travel_time + times("00:00:40")))),
    by = trip_id]

dt2

 #   trip_id stop_sequence arrival_time departure_time travel_time
 #1:       a             1     07:00:00       07:00:00    00:00:00
 #2:       a             2     07:02:41       07:03:21    00:02:41
 #3:       a             3     07:04:57       07:05:37    00:01:36
 #4:       a             4     07:08:16       07:08:56    00:02:39
 #5:       a             5     07:11:24       07:12:04    00:02:28
 #6:       b             1     07:00:00       07:00:00    00:00:00
 #7:       b             2     07:00:45       07:01:25    00:00:45
 #8:       b             3     07:03:01       07:03:41    00:01:36
 #9:       b             4     07:04:18       07:04:58    00:00:37
#10:       b             5     07:07:58       07:08:38    00:03:00

或者，您也不必为cumsum重复departure_time长arrival_time来获取dt2[,departure_time := cumsum(arrival_time + ifelse(travel_time==0, 0, travel_time + times("00:00:40"))), by = trip_id] dt2[, arrival_time := departure_time - ifelse(travel_time == 0 , 0, times("00:00:40"))]：

dt[, departure_time := arrival_time[1] + cumsum(travel_time) + (0:(.N-1))*times('00:00:40'), by = trip_id]
dt[, arrival_time := c(arrival_time[1], tail(departure_time, -1) - times('00:00:40')), by = trip_id]

@eddi发布的第三个选项：

  sendValueToParentForModification(e) {
//Send the value to parent
this.sendValue.emit({ childComponent: this, e: e, myValue: this.myValue });
/*
The parent modifies the value and that modified value should be used here.. 
Right now, I'm having the parent component call the function in this child "useModifiedValue".
Instead, I want the flow to somehow come over here.. so that I can call the 
"useModifiedValue" function right here, with the modified value. How to do this?
*/

使用data.table更新两个相互依赖的列

1 个答案: