假设我有一个数据框
假设我有一个数据框
> data
session id timestamp item id
1 2014-04-0618:42:05.822 1
1 2014-04-0618:42:06.800 1
1 2014-04-0618:42:06.820 1
2 2014-04-0315:27:48.118 1
2 2014-04-0315:27:49.440 2
3 2014-04-0315:27:49.550 1
3 2014-04-0315:27:50.240 0
3 2014-04-0315:27:50.540 3
3 2014-04-0315:27:51.530 2
我想找出每个会话的开始和结束时间以及每个会话中的唯一项目意味着我想要这样的输出
> result
session id session start and end time distinctitems in each session
1 2014-04-0618:42:05.822, 2014-04-0618:42:06.820 1
2 2014-04-0315:27:48.118, 2014-04-0315:27:49.440 2
3 2014-04-0315:27:49.550, 2014-04-0315:27:51.530 4
我怎样才能做到这一点？