r - 同一列内的差异时间

Question

数据框是这样的：

db = (name = c('A','A','A', 'B','B','B','B', 'C','C'),
      time = c('09/09/15 0:37:45', '09/09/15 0:39:45', '09/09/15 1:39:15', '09/10/15'20:35:20, '09/10/15 20:45:40', '09/10/15 20:47:00', '09/10/15 21:47:00' ,'09/11/15 7:15:15', '09/11/15 17:15:30')

我想要得到的是每个名字之间的分钟时间间隔，我想要得到的数据是这样的：

db = (name = c('A','A','A', 'B','B','B','B', 'C','C'),
      gap = c(NA, 2, 59.5, NA, 10.33, 1.67, 60, NA, 600.25)

任何人都可以解决这个难题吗？谢谢！

Answer 1

library(dplyr)
db %>% group_by(name) %>% mutate(gap=round(c(NA,diff(time)), 1))
Source: local data frame [9 x 3]
Groups: name [3]

    name                time   gap
  (fctr)              (time) (dbl)
1      A 2015-09-09 00:37:45    NA
2      A 2015-09-09 00:39:45   2.0
3      A 2015-09-09 01:39:15  59.5
4      B 2015-09-10 20:35:20    NA
5      B 2015-09-10 20:45:40  10.3
6      B 2015-09-10 20:47:00   1.3
7      B 2015-09-10 21:47:00  60.0
8      C 2015-09-11 07:15:15    NA
9      C 2015-09-11 17:15:30  10.0