按日期为每个组添加订购 ID

Question

我想为数据框中的每个组添加一个有序 ID（按日期）。我可以使用 dplyr ():

# Example data
date <- rep(c("2016-10-06 11:56:00","2016-10-05 11:56:00","2016-10-05 11:56:00","2016-10-07 11:56:00"),2)
date <- as.POSIXct(date)
group <- c(rep("A",4), rep("B",4))    
df <- data.frame(group, date)

# dplyr - dense_rank
df2 <- df %>% group_by(group) %>% 
       mutate(m.test=dense_rank(date))

   group                date m.test
  <fctr>              <dttm>  <int>
1      A 2016-10-06 11:56:00      2
2      A 2016-10-05 11:56:00      1
3      A 2016-10-05 11:56:00      1
4      A 2016-10-07 11:56:00      3
5      B 2016-10-06 11:56:00      2
6      B 2016-10-05 11:56:00      1
7      B 2016-10-05 11:56:00      1
8      B 2016-10-07 11:56:00      3

所以我的新专栏 m.test 将每个 group 排名 date。如果我用rleid和data.table，好像不行（05/10排在06/10之后）：

df3 <- setDT(df)[, m.test := rleid(date), by = group]

   group                date m.test
1:     A 2016-10-06 11:56:00      1
2:     A 2016-10-05 11:56:00      2
3:     A 2016-10-05 11:56:00      2
4:     A 2016-10-07 11:56:00      3
5:     B 2016-10-06 11:56:00      1
6:     B 2016-10-05 11:56:00      2
7:     B 2016-10-05 11:56:00      2
8:     B 2016-10-07 11:56:00      3

我的语法有误吗？

Answer 1

感谢@docendo discimus，使用 data.table 执行此操作的正确方法是 frank(..., ties.method = "dense"):

df4 <- setDT(df)[, m.test := frank(date, ties.method = "dense"), by = group]

按日期为每个组添加订购 ID

Add ordered ID for each group by date

r

rank

data.table