r - dplyr:在group_by中生成行号/行位置

Question

我有一个数据集，我想按组生成行位置。例如

library(data.table)

data<-data.table(Position=c(1,2,3,4,5,6,7,8,9,10),
Category=c("M","M","M","M","F","F","F","M","M","F"))

我按类别分组，并希望创建作为按组的行位置的列。类似于下面或 data.table 的内容

dataByGroup %>% group_by(Category) %>% mutate(positionInCategory = 1:nrow(Category))

无法弄清楚如何实现这一目标？

期望的输出:

| Position|Category | positionInCategory|
|--------:|:--------|------------------:|
|        1|M        |                  1|
|        2|M        |                  2|
|        3|M        |                  3|
|        4|M        |                  4|
|        5|F        |                  1|
|        6|F        |                  2|
|        7|F        |                  3|
|        8|M        |                  5|
|        9|M        |                  6|
|       10|F        |                  4|

Answer 1

尝试以下操作:

library(data.table)
library(dplyr)

data<-data.table(Position=c(1,2,3,4,5,6,7,8,9,10),
                 Category=c("M","M","M","M","F","F","F","M","M","F"))

cleanData <- data %>%
  group_by(Category) %>%
  mutate(positionInCategory = 1:n())