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Identify groups

Source: R/group.R
vec_group.Rd

[Experimental]

  • vec_group_id() returns an identifier for the group that each element of x falls in, constructed in the order that they appear. The number of groups is also returned as an attribute, n.

  • vec_group_loc() returns a data frame containing a key column with the unique groups, and a loc column with the locations of each group in x.

  • vec_group_rle() locates groups in x and returns them run length encoded in the order that they appear. The return value is a rcrd object with fields for the group identifiers and the run length of the corresponding group. The number of groups is also returned as an attribute, n.

Usage

vec_group_id(x)

vec_group_loc(x)

vec_group_rle(x)

Arguments

x

A vector

Value

  • vec_group_id(): An integer vector with the same size as x.

  • vec_group_loc(): A two column data frame with size equal to vec_size(vec_unique(x)).

    • A key column of type vec_ptype(x)

    • A loc column of type list, with elements of type integer.

  • vec_group_rle(): A vctrs_group_rle rcrd object with two integer vector fields: group and length.

Note that when using vec_group_loc() for complex types, the default data.frame print method will be suboptimal, and you will want to coerce into a tibble to better understand the output.

Dependencies

Examples

purrr <- c("p", "u", "r", "r", "r")
vec_group_id(purrr)
#> [1] 1 2 3 3 3
#> attr(,"n")
#> [1] 3
vec_group_rle(purrr)
#> <vctrs_group_rle[3][n = 3]>
#> [1] 1x1 2x1 3x3

groups <- mtcars[c("vs", "am")]
vec_group_id(groups)
#>  [1] 1 1 2 3 4 3 4 3 3 3 3 4 4 4 4 4 4 2 2 2 3 4 4 4 4 2 1 2 1 1 1 2
#> attr(,"n")
#> [1] 4

group_rle <- vec_group_rle(groups)
group_rle
#> <vctrs_group_rle[16][n = 4]>
#>  [1] 1x2 2x1 3x1 4x1 3x1 4x1 3x4 4x6 2x3 3x1 4x4 2x1 1x1 2x1 1x3 2x1

# Access fields with `field()`
field(group_rle, "group")
#>  [1] 1 2 3 4 3 4 3 4 2 3 4 2 1 2 1 2
field(group_rle, "length")
#>  [1] 2 1 1 1 1 1 4 6 3 1 4 1 1 1 3 1

# `vec_group_id()` is equivalent to
vec_match(groups, vec_unique(groups))
#>  [1] 1 1 2 3 4 3 4 3 3 3 3 4 4 4 4 4 4 2 2 2 3 4 4 4 4 2 1 2 1 1 1 2

vec_group_loc(mtcars$vs)
#>   key                                                                loc
#> 1   0 1, 2, 5, 7, 12, 13, 14, 15, 16, 17, 22, 23, 24, 25, 27, 29, 30, 31
#> 2   1                  3, 4, 6, 8, 9, 10, 11, 18, 19, 20, 21, 26, 28, 32
vec_group_loc(mtcars[c("vs", "am")])
#>   key.vs key.am                                          loc
#> 1      0      1                         1, 2, 27, 29, 30, 31
#> 2      1      1                    3, 18, 19, 20, 26, 28, 32
#> 3      1      0                       4, 6, 8, 9, 10, 11, 21
#> 4      0      0 5, 7, 12, 13, 14, 15, 16, 17, 22, 23, 24, 25

if (require("tibble")) {
  as_tibble(vec_group_loc(mtcars[c("vs", "am")]))
}
#> # A tibble: 4 × 2
#>   key$vs   $am loc       
#>    <dbl> <dbl> <list>    
#> 1      0     1 <int [6]> 
#> 2      1     1 <int [7]> 
#> 3      1     0 <int [7]> 
#> 4      0     0 <int [12]>