根据组添加计数器

问题描述

我正在尝试将计数器列（n_team和n_bird）添加到数据帧，而对dplyr::row_number等没有成功。下面是一个带有输入数据帧（df）和所需的输出数据帧（df_counts）的reprex，以及一些错误输出的代码。

谢谢您的帮助！

library(dplyr)

# Input
df <- 
  tribble(
    ~id,~team,~bird,1,"blue","parrot",2,"green","owl",3,"toucan","finch",4,"penguin","sparrow"
  )

# Desired output
# n_team is the team number within an id
# n_bird is the bird number within a team within an id
df_counts <- 
  tribble(
    ~id,~n_team,~n_bird,"sparrow",1
  )

# Incorrect
df %>% 
  add_count(id,team,name = "n_team")
#> # A tibble: 6 x 4
#>      id team  bird    n_team
#>   <dbl> <chr> <chr>    <int>
#> 1     1 blue  parrot       1
#> 2     2 green owl          1
#> 3     3 blue  toucan       2
#> 4     3 blue  finch        2
#> 5     4 green penguin      1
#> 6     4 blue  sparrow      1

df %>% 
  group_by(id) %>% 
  mutate(n_team =  row_number(team))
#> # A tibble: 6 x 4
#> # Groups:   id [4]
#>      id team  bird    n_team
#>   <dbl> <chr> <chr>    <int>
#> 1     1 blue  parrot       1
#> 2     2 green owl          1
#> 3     3 blue  toucan       1
#> 4     3 blue  finch        2
#> 5     4 green penguin      2
#> 6     4 blue  sparrow      1

df %>% 
  group_by(id,team) %>% 
  mutate(n_team =  1:n())
#> # A tibble: 6 x 4
#> # Groups:   id,team [5]
#>      id team  bird    n_team
#>   <dbl> <chr> <chr>    <int>
#> 1     1 blue  parrot       1
#> 2     2 green owl          1
#> 3     3 blue  toucan       1
#> 4     3 blue  finch        2
#> 5     4 green penguin      1
#> 6     4 blue  sparrow      1

df %>% 
  group_by(id) %>% 
  mutate(n_team =  n_distinct(team))
#> # A tibble: 6 x 4
#> # Groups:   id [4]
#>      id team  bird    n_team
#>   <dbl> <chr> <chr>    <int>
#> 1     1 blue  parrot       1
#> 2     2 green owl          1
#> 3     3 blue  toucan       1
#> 4     3 blue  finch        1
#> 5     4 green penguin      2
#> 6     4 blue  sparrow      2

df %>% 
  add_count(team)
#> # A tibble: 6 x 4
#>      id team  bird        n
#>   <dbl> <chr> <chr>   <int>
#> 1     1 blue  parrot      4
#> 2     2 green owl         2
#> 3     3 blue  toucan      4
#> 4     3 blue  finch       4
#> 5     4 green penguin     2
#> 6     4 blue  sparrow     4

# Counts alphabetically
df %>% 
  group_by(id,team) %>% 
  mutate(n_bird =  row_number(bird))
#> # A tibble: 6 x 4
#> # Groups:   id,team [5]
#>      id team  bird    n_bird
#>   <dbl> <chr> <chr>    <int>
#> 1     1 blue  parrot       1
#> 2     2 green owl          1
#> 3     3 blue  toucan       2
#> 4     3 blue  finch        1
#> 5     4 green penguin      1
#> 6     4 blue  sparrow      1

# Counts in order
df %>% 
  group_by(id,team) %>% 
  mutate(n_bird =  row_number())
#> # A tibble: 6 x 4
#> # Groups:   id,team [5]
#>      id team  bird    n_bird
#>   <dbl> <chr> <chr>    <int>
#> 1     1 blue  parrot       1
#> 2     2 green owl          1
#> 3     3 blue  toucan       1
#> 4     3 blue  finch        2
#> 5     4 green penguin      1
#> 6     4 blue  sparrow      1

^{由reprex package（v0.3.0）于2020-09-04创建}

以下是我咨询过的一些资源：

• add counter column by arranging two variables (dplyr)
• https://community.rstudio.com/t/how-to-add-a-counter-to-each-group-in-dplyr/12986/2
• https://dplyr.tidyverse.org/reference/tally.html
• https://dplyr.tidyverse.org/reference/n_distinct.html

解决方法

这里有4种非常相似但又不同的方法：

1. match + unique：

library(dplyr)
df %>%
  group_by(id) %>%
  mutate(n_teams = match(team,unique(team))) %>%
  group_by(team,.add = TRUE) %>%
  mutate(n_bird =  match(bird,unique(bird)))

#    id team  bird    n_teams n_bird
#  <dbl> <chr> <chr>     <int>  <int>
#1     1 blue  parrot        1      1
#2     2 green owl           1      1
#3     3 blue  toucan        1      1
#4     3 blue  finch         1      2
#5     4 green penguin       1      1
#6     4 blue  sparrow       2      1

1. factor + as.integer：

df %>%
  group_by(id) %>%
  mutate(n_teams = as.integer(factor(team))) %>%
  group_by(team,.add = TRUE) %>%
  mutate(n_bird =  as.integer(factor(bird)))

1. data.table::rleid

df %>%
  group_by(id) %>%
  mutate(n_teams = data.table::rleid(team)) %>%
  group_by(team,.add = TRUE) %>%
  mutate(n_bird =  data.table::rleid(bird))

1. dense_rank：

df %>%
  group_by(id) %>%
  mutate(n_teams = dense_rank(team)) %>%
  group_by(team,.add = TRUE) %>%
  mutate(n_bird =  dense_rank(bird))

,

这是一种可能的方法：

df %>%
    group_by(id) %>%
    mutate(n_teams = cumsum(!duplicated(team))) %>%
    group_by(id,team) %>%
    mutate(n_bird = cumsum(!duplicated(bird))) %>%
    ungroup()

,

data.table版本

library(data.table)
setDT(df)

df[,n_team := match(team,unique(team)),id]
df[,n_bird := 1:.N,.(id,team)]
df

#>    id  team    bird n_team n_bird
#> 1:  1  blue  parrot      1      1
#> 2:  2 green     owl      1      1
#> 3:  3  blue  toucan      1      1
#> 4:  3  blue   finch      1      2
#> 5:  4 green penguin      1      1
#> 6:  4  blue sparrow      2      1