dplyr：在group_by中生成行号/行位置 [英] dplyr: Generate row number/row position in group_by

问题描述

我有一个数据集，我想按组生成行位置。例如

I have a dataset and I want to generate the row position by group. For example

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，并想按组创建作为行位置的列。像下面这样或带有data.table的东西

I group by the Category and want to create column that is the row position by group. Something like below or with data.table

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

无法计算出该如何实现？

Unable to work out how to achieve this?

所需的输出：

| 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|

推荐答案

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())

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