Join columns, duplicating existing row for each variable in new column

May 24, 2022

Ok so say we have two different columns of data. One is just a running date column:

The other is just an ID column

ID
asdflauih3298b43f9n
akjwn3ibfun9834n93n
nv43879n4vliuhs87ba

I would like to join these columns in a way so that each ID occurs for every day. Like this:

day            ID
2017-11-08     asdflauih3298b43f9n  
2017-11-08     akjwn3ibfun9834n93n
2017-11-08     nv43879n4vliuhs87ba  
2017-11-09     asdflauih3298b43f9n  
2017-11-09     akjwn3ibfun9834n93n      
2017-11-09     nv43879n4vliuhs87ba              
2017-11-10     asdflauih3298b43f9n  
2017-11-10     akjwn3ibfun9834n93n
2017-11-10     nv43879n4vliuhs87ba

Looking to do this in tidyverse. I know this should be really easy, but I’m stumped. Thanks!

>Solution :

You can use the regular joining functions from dplyr to perform a cross-join like this by setting the by argument to character():

library(dplyr)

left_join(A, B, by = character())

#> # A tibble: 18 × 2
#>    day        ID                 
#>    <chr>      <chr>              
#>  1 2017-11-08 asdflauih3298b43f9n
#>  2 2017-11-08 akjwn3ibfun9834n93n
#>  3 2017-11-08 nv43879n4vliuhs87ba
#>  4 2017-11-09 asdflauih3298b43f9n
#>  5 2017-11-09 akjwn3ibfun9834n93n
#>  6 2017-11-09 nv43879n4vliuhs87ba
#>  7 2017-11-10 asdflauih3298b43f9n
#>  8 2017-11-10 akjwn3ibfun9834n93n
#>  9 2017-11-10 nv43879n4vliuhs87ba
#> 10 2017-11-13 asdflauih3298b43f9n
#> 11 2017-11-13 akjwn3ibfun9834n93n
#> 12 2017-11-13 nv43879n4vliuhs87ba
#> 13 2017-11-14 asdflauih3298b43f9n
#> 14 2017-11-14 akjwn3ibfun9834n93n
#> 15 2017-11-14 nv43879n4vliuhs87ba
#> 16 2017-11-15 asdflauih3298b43f9n
#> 17 2017-11-15 akjwn3ibfun9834n93n
#> 18 2017-11-15 nv43879n4vliuhs87ba

^{Created on 2022-05-24 by the reprex package (v2.0.1)}

Data

A <- tibble::tribble(
  ~day,
  "2017-11-08",              
  "2017-11-09",              
  "2017-11-10",              
  "2017-11-13",              
  "2017-11-14",              
  "2017-11-15"  
)

B <- tibble::tribble(
  ~ID,
  "asdflauih3298b43f9n",
  "akjwn3ibfun9834n93n",
  "nv43879n4vliuhs87ba"
)