diff
時間通りに実行してから、3 番目の列にデータid
を入力する必要がありますifelse
df <- structure(list(id = c(1L, 1L, 1L, 2L, 2L, 2L),
time = structure(c(1359915659, 1359915665, 1359915684,
1359915686, 1359915739, 1359915755), class = c("POSIXct",
"POSIXt"), tzone = "")), .Names = c("id", "time"), row.names = c(NA, -6L),
class = "data.frame")
df
## id time
## 1 1 2013-02-04 02:20:59
## 2 1 2013-02-04 02:21:05
## 3 1 2013-02-04 02:21:24
## 4 2 2013-02-04 02:21:26
## 5 2 2013-02-04 02:22:19
## 6 2 2013-02-04 02:22:35
## here you are checking if that result is diff in time only when diff in id is 0
df$result <- c(0, ifelse(diff(df$id) == 0, diff(df$time), 0))
df
## id time result
## 1 1 2013-02-04 02:20:59 0
## 2 1 2013-02-04 02:21:05 6
## 3 1 2013-02-04 02:21:24 19
## 4 2 2013-02-04 02:21:26 0
## 5 2 2013-02-04 02:22:19 53
## 6 2 2013-02-04 02:22:35 16