Question

我有2张桌子，如下所示。在表1中，“开始”和“结束”为每个键定义了一段时间。

任务是将表2中的时间戳与第一张表的相应时间段进行匹配，检索关联的键并将其分配给时间戳。

到目前为止，我发现between()::lubridate对测试时间戳是否在该时段内很有用。 between()的输出是逻辑向量。我认为如果值为TRUE，代码就可以工作，但是如果时间戳不匹配任何周期（即值为FALSE），则代码会失败。

有人知道如何解决吗？

# generate tables

Keys = c("F11-47" , "F11-49" , "F11-66" )
Start = c("2018-01-15 11:35:00" ,"2018-01-23 12:05:00" , "2018-10-09 11:44:00" )
End = c("2018-01-23 04:05:00", "2018-05-15 13:32:03", "2018-12-10 05:06:00")

table1 = as.data.frame(cbind(Keys, Start, End))
table1$Start = ymd_hms(table1$Start) # parse to POSIX
table1$End = ymd_hms(table1$End) # parse to POSIX

timestamps = c("2018-01-16 11:37:00", "2019-04-26 16:13:05" , "2018-01-19 15:35:00", "2018-01-23 12:05:00", "2018-01-24 12:05:00" ,"2018-02-24 12:05:00" , 
               "2018-03-23 12:15:00", "2017-10-03 14:11:01" , "2018-04-07 14:15:00", "2018-10-17 14:15:00" , "2018-11-01 5:33:16", "2019-03-26 16:18:27"  )

table2 = as.data.frame(timestamps)
table2$Keys = ""
table2$timestamps = ymd_hms(table2$timestamps) # parse to POSIX

# what I've done so far

for (i in 1:length(table2$timestamps)) {

  timestamp = table2$timestamps[i]

   for (j in 1:length(table1$Keys)) {

    if (between(timestamp, table1$Start[j], table1$End[j])) {  # test if timestamp is between a time period

      expkey = table1$Exp_Keys[j]  # retrieve Key from that time period
    }

  }

  table2$Keys[i] = expkey  # assign key to timestamp

}

Answer 1

在指示的条件下执行左联接：

library(sqldf)

sqldf("select t2.timestamps, t1.Keys
  from table2 t2 
  left join table1 t1 on t2.timestamps between t1.Start and t1.End")

给予：

            timestamps   Keys
1  2018-01-16 06:37:00 F11-47
2  2019-04-26 12:13:05   <NA>
3  2018-01-19 10:35:00 F11-47
4  2018-01-23 07:05:00 F11-49
5  2018-01-24 07:05:00 F11-49
6  2018-02-24 07:05:00 F11-49
7  2018-03-23 08:15:00 F11-49
8  2017-10-03 10:11:01   <NA>
9  2018-04-07 10:15:00 F11-49
10 2018-10-17 10:15:00 F11-66
11 2018-11-01 01:33:16 F11-66
12 2019-03-26 12:18:27   <NA>

如何将时间戳与R中的时间段进行匹配

1 个答案: