Is there a way to not expand one column while expanding others?

user_7545285 0
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I have a with users, the groups they belong to, and two columns I want to expand (below). I want to expand it so that each user keeps the groups that they're in but for each group they're in gets all possible permutations of country and season.

User_ID Group Country Season
1 1 France Autumn
2 2 Spain Summer
1 2 Italy Winter
3 2 Italy Spring

Currently I'm expanding all of the columns then doing a semi-join to the table to drop all of the user and group combinations which don't exist.

df <- data.frame(User_ID = c(1, 2, 1, 3), 
    Group = c(1,2,2,1), 
    Country = c("France", "Spain", "Italy","Italy"), 
    Season = c("Summer", "Autumn", "Winter", "Spring")) 

df %>% 
    expand(User_ID, Group, Country, Season) %>%
    semi_join(df, by = c("User_ID", "Group")

Is this the most efficient way to do this, or am I missing something with the expand function?

tidyverse r
1 Answers

Is this what you want (4 user/groups x 3 countries x 4 seasons, i.e. 48 rows)?

library(tidyverse)

tribble(
  ~User_ID, ~Group, ~Country, ~Season,
  1, 1, "France", "Autumn",
  2, 2, "Spain", "Summer",
  1, 2, "Italy", "Winter",
  3, 2, "Italy", "Spring"
) |> 
  complete(nesting(User_ID, Group), Country, Season)

#> # A tibble: 48 × 4
#>    User_ID Group Country Season
#>      <dbl> <dbl> <chr>   <chr> 
#>  1       1     1 France  Autumn
#>  2       1     1 France  Spring
#>  3       1     1 France  Summer
#>  4       1     1 France  Winter
#>  5       1     1 Italy   Autumn
#>  6       1     1 Italy   Spring
#>  7       1     1 Italy   Summer
#>  8       1     1 Italy   Winter
#>  9       1     1 Spain   Autumn
#> 10       1     1 Spain   Spring
#> # … with 38 more rows

Created on 2022-06-14 by the reprex package (v2.0.1)

user_73270580
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