Run-length-encoding, making groups

rle-groups.R

## Using run-length-encoding, create groups of identical values and put that
## common grouping identifier into a `grp` column.
library(tidyverse)

set.seed(42)

df <- tibble(x = sample(c(0,1), size=20, replace=TRUE, prob = c(0.2, 0.8)))

df %>%
    mutate(grp = rle(x)$lengths %>% {rep(seq(length(.)), .)})
#> # A tibble: 20 x 2
#>        x   grp
#>    <dbl> <int>
#>  1     0     1
#>  2     0     1
#>  3     1     2
#>  4     0     3
#>  5     1     4
#>  6     1     4
#>  7     1     4
#>  8     1     4
#>  9     1     4
#> 10     1     4
#> 11     1     4
#> 12     1     4
#> 13     0     5
#> 14     1     6
#> 15     1     6
#> 16     0     7
#> 17     0     7
#> 18     1     8
#> 19     1     8
#> 20     1     8