How to apply a visit names to subject IDs using data from two tables

I have two tables the first is a single column with Subject Ids and the second is a single column with the Visit Names

library(tibble)

subjects <- tibble("Subject Id" = c("1-1", "1-2", "1-3"))

# A tibble: 3 x 1
  `Subject Id`
  <chr>       
1 1-1         
2 1-2         
3 1-3)
                   
visits <- tibble("Visits" = c("a", "b", "c"))

# A tibble: 3 x 1
  Visits
  <chr> 
1 a     
2 b     
3 c 

And I want to create a table that looks like this so I see every potential visit for every subject.

I’ve been trying to find a good solution, but all of the similar questions I find go back to doing a merge and that doesn’t seem like the correct solution for what I want to do.

>Solution :

We can use crossing

library(tidyr)
crossing(subjects, visits)

-output

# A tibble: 9 × 2
  `Subject Id` Visits
  <chr>        <chr> 
1 1-1          a     
2 1-1          b     
3 1-1          c     
4 1-2          a     
5 1-2          b     
6 1-2          c     
7 1-3          a     
8 1-3          b     
9 1-3          c     

Or using base R

 expand.grid(c(subjects, visits))
  Subject Id Visits
1        1-1      a
2        1-2      a
3        1-3      a
4        1-1      b
5        1-2      b
6        1-3      b
7        1-1      c
8        1-2      c
9        1-3      c