How to use tidyr::crossing function-CodePudding

There is a function called tidyr::crossing

As per the help function, it does this: ‘crossing()’ is a wrapper around ‘expand_grid()’ that de-duplicates and sorts its inputs

However when I tried to compare expand.grid() and crossing() I don't see they are retiring similar values:

> expand.grid(list(1:4, 1:4))
   Var1 Var2
1     1    1
2     2    1
3     3    1
4     4    1
5     1    2
6     2    2
7     3    2
8     4    2
9     1    3
10    2    3
11    3    3
12    4    3
13    1    4
14    2    4
15    3    4
16    4    4
> tidyr::crossing(list(1:4, 1:4))
# A tibble: 1 × 1
  `list(1:4, 1:4)`
  <list>          
1 <int [4]>

Could you please help me to understand what crossing() function exactly does? In there help page, there seem to have no example

CodePudding user response：

If you use vectors instead of lists, you see why they are pretty much the same but with additional sorting and deduplication:

tidyr::crossing(
  a = 1:3,
  b = 1:3
)
#> # A tibble: 9 x 2
#>       a     b
#>   <int> <int>
#> 1     1     1
#> 2     1     2
#> 3     1     3
#> 4     2     1
#> 5     2     2
#> 6     2     3
#> 7     3     1
#> 8     3     2
#> 9     3     3

tidyr::expand_grid(
  a = 1:3,
  b = 1:3
)
#> # A tibble: 9 x 2
#>       a     b
#>   <int> <int>
#> 1     1     1
#> 2     1     2
#> 3     1     3
#> 4     2     1
#> 5     2     2
#> 6     2     3
#> 7     3     1
#> 8     3     2
#> 9     3     3


set.seed(1)
c <- sample(seq(4))
c
#> [1] 1 3 4 2

tidyr::crossing(a = 1:3, c)
#> # A tibble: 12 x 2
#>        a     c
#>    <int> <int>
#>  1     1     1
#>  2     1     2
#>  3     1     3
#>  4     1     4
#>  5     2     1
#>  6     2     2
#>  7     2     3
#>  8     2     4
#>  9     3     1
#> 10     3     2
#> 11     3     3
#> 12     3     4
tidyr::expand_grid(a = 1:3, c)
#> # A tibble: 12 x 2
#>        a     c
#>    <int> <int>
#>  1     1     1
#>  2     1     3
#>  3     1     4
#>  4     1     2
#>  5     2     1
#>  6     2     3
#>  7     2     4
#>  8     2     2
#>  9     3     1
#> 10     3     3
#> 11     3     4
#> 12     3     2

^{Created on 2021-09-30 by the reprex package (v2.0.1)}

expand_grid is the tidyverse verision of expand.grid and returns a tibble instead of a data.frame.