Finding value +1 within a group

Emma Doughty

I have a large dataframe that I have grouped by Date. Within each date group, I'd like to keep the rows for rooms that are next door to one another, i.e. Room.num = any Room.num in group +/- 1

 Date        Room.num  
1 2019.08.21  1  
2 2019.08.21  2  
3 2020.07.18  6  
4 2020.07.18  1  
5 2020.07.18  3

I want to end up with just

  Date        Room.num  
1 2019.08.21  1  
2 2019.08.21  2

I have tried

df %>% 
   group_by(Date)
   filter(Room.num=1)

which gives me

Date Room.num
1 2019.08.21 1
4 2020.07.18 1

I have also tried

df %>% 
   group_by(Date)
   filter(any(Room.num=1))

This gives me

  Date        Room.num  
1 2019.08.21  1  
2 2019.08.21  2  
3 2020.07.18  6  
4 2020.07.18  1  
5 2020.07.18  3

i.e. any group with a Room.num=1

But I am not able to do what I want keep rows whichhave a room number that is +/- 1 of any other Room.num in that Date group

df %>% 
   group_by(Date)
   filter(Room.num==any(Room.num)+1)

I get

Date        Room.num  
2 2019.08.21  2

The second Room.num is always = 1

AnilGoyal

I think you can do this in tidyverse

df <- read.table(header = T, text = 'Date Room.num
1 2019.08.21 1
2 2019.08.21 2
3 2020.07.18 6
4 2020.07.18 1
5 2020.07.18 3
')

library(tidyverse)
df  %>%
  group_by(Date) %>%
  filter(map_lgl(Room.num, ~ .x %in% c(Room.num -1, Room.num +1))) %>%
  ungroup()
#> # A tibble: 2 x 2
#>   Date       Room.num
#>   <chr>         <int>
#> 1 2019.08.21        1
#> 2 2019.08.21        2

If you, however, want to avoid purrr::map_lgl use this similar baseR function like this

df  %>%
  group_by(Date) %>%
  filter(unlist(Map(\(.x) .x %in% c(Room.num -1, Room.num +1), Room.num))) %>%
  ungroup()

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edited at2021-07-25

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Finding value +1 within a group

Finding value +1 within a group

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