我有以下数据框:
Time Work
2018-12-01 10:00:00 Off
2018-12-01 10:00:02 On
2018-12-01 10:00:05 On
2018-12-01 10:00:06 On
2018-12-01 10:00:07 On
2018-12-01 10:00:09 Off
2018-12-01 10:00:11 Off
2018-12-01 10:00:14 On
2018-12-01 10:00:16 On
2018-12-01 10:00:18 On
2018-12-01 10:00:20 Off
我想创建一个新的列,用于记录设备启动后经过的时间。
Time Work Elapsed Time
2018-12-01 10:00:00 Off 0
2018-12-01 10:00:02 On 2
2018-12-01 10:00:05 On 5
2018-12-01 10:00:06 On 6
2018-12-01 10:00:07 On 7
2018-12-01 10:00:09 Off 0
2018-12-01 10:00:11 Off 0
2018-12-01 10:00:14 On 3
2018-12-01 10:00:16 On 5
2018-12-01 10:00:18 On 7
2018-12-01 10:00:20 Off 0
我该怎么做?