Question

我想在数据框中为每个组添加一个有序ID（按日期）。我可以使用dplyr（R - add column that counts sequentially within groups but repeats for duplicates）执行此操作：

Create index abc
Snapshot index abc
Delete index abc
-----
Create index abc (again)
Snapshot index abc
Delete index abc

因此，我的新专栏# 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按m.test对每个group进行排名。如果我使用date和rleid，它似乎不起作用（05/10在06/10之后排名）：

data.table

我的语法错误了吗？

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]

使用rleid按日期为每个组添加有序ID

1 个答案: