按组计算连续天数

Question

我希望添加一个字段来计算每个组内的连续天数（由 id 字段捕获）。我从这个开始：

dt <- structure(list(id = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), date = c("1/01/2000", "2/01/2000", "2/01/2000", 
"5/01/2000", "6/01/2000", "7/01/2000", "8/01/2000", "13/01/2000", "14/01/2000", 
"18/01/2000", "19/01/2000", "21/01/2000", "25/01/2000", "26/01/2000", 
"30/01/2000", "31/01/2000")), .Names = c("id", "date"), 
row.names = c(NA, -16L), class = "data.frame")

并希望获得以下内容，最好使用 data.table：

id date       cons
1  1/01/2000  0
1  2/01/2000  1
1  2/01/2000  1
1  5/01/2000  0
1  6/01/2000  1
1  7/01/2000  2
1  8/01/2000  3
2 13/01/2000  0
2 14/01/2000  1
2 18/01/2000  0
2 19/01/2000  1
2 21/01/2000  0
2 25/01/2000  0
2 26/01/2000  1
2 30/01/2000  0
2 31/01/2000  1

Answer 1

这是一种使用方法dplyr

library(dplyr)

dt %>%
  mutate(date = as.Date(date, "%d/%m/%Y")) %>%
  group_by(id) %>%
  group_by(grp = cumsum(c(TRUE, diff(date) > 1)), add = TRUE) %>%
  mutate(cons = as.integer(date - first(date))) %>%
  ungroup %>%
  select(-grp)

#      id date        cons
#   <int> <date>     <int>
# 1     1 2000-01-01     0
# 2     1 2000-01-02     1
# 3     1 2000-01-02     1
# 4     1 2000-01-05     0
# 5     1 2000-01-06     1
# 6     1 2000-01-07     2
# 7     1 2000-01-08     3
# 8     2 2000-01-13     0
# 9     2 2000-01-14     1
#10     2 2000-01-18     0
#11     2 2000-01-19     1
#12     2 2000-01-21     0
#13     2 2000-01-25     0
#14     2 2000-01-26     1
#15     2 2000-01-30     0
#16     2 2000-01-31     1

正如您标记的那样data.table，同样可以翻译为data.table

library(data.table)

setDT(dt)
dt[, date := as.Date(date, "%d/%m/%Y")]
dt[, cons := as.integer(date - first(date)), .(id, cumsum(c(TRUE, diff(date) > 1)))]