如何在R中复制行并添加新数据?

I have a data.table of timestamp data that has both time in and time out for people, rounded to the nearest 15 minute intervals. I want to be able to duplicate each row to have the same number of copies as the number of 15 minute intervals their time-in/time-out data covers, while adding a new column that lists the 15 minute interval (e.g. given a person clocking in at 10:00am and clocking out at 11:00am, there would be four rows made, one with time saying 10:00am, one saying 10:15am, one saying 10:30am, and one saying 10:45am).I have a data.table of timestamp data that has