I would like to separate a field using tidyr:separate and keep the separator and use negative look back - tidyr

Question

I would like to use separate with a negative look behind and keep the separator. My solution
below does not keep the first capital letter of the last name.
There is an answer that does not use negative and I can't figure out how to modify it for
negative look back.
How do I split a string with tidyr::separate in R and retain the values of the separator string?
tidyr::tibble(myname = c("HarlanNelson")) |>
tidyr::separate(col = myname, into = c("first", "last"), sep = "(?<!^)[[:upper:]]")
#> # A tibble: 1 × 2
#> first last
#> <chr> <chr>
#> 1 Harlan elson
Created on 2022-10-20 by the reprex package (v2.0.1)
tidyr::tibble(myname = c("HarlanNelson", "Another Person")) |>
tidyr::separate(col = myname, into = c("first", "last"), sep = c(" ", "(?<!^)[[:upper:]]"))
#> Warning in gregexpr(pattern, x, perl = TRUE): argument 'pattern' has length > 1
#> and only the first element will be used
#> Warning: Expected 2 pieces. Missing pieces filled with `NA` in 1 rows [1].
#> # A tibble: 2 × 2
#> first last
#> <chr> <chr>
#> 1 HarlanNelson <NA>
#> 2 Another Person
Created on 2022-10-20 by the reprex package (v2.0.1)
tidyr::tibble(myname = c("HarlanNelson", "Another Person", "someone else")) |>
tidyr::separate(col = myname, into = c("first", "last"), sep = c(" ", "(?<!^)[[:upper:]]"))
#> Warning in gregexpr(pattern, x, perl = TRUE): argument 'pattern' has length > 1
#> and only the first element will be used
#> Warning: Expected 2 pieces. Missing pieces filled with `NA` in 1 rows [1].
#> # A tibble: 3 × 2
#> first last
#> <chr> <chr>
#> 1 HarlanNelson <NA>
#> 2 Another Person
#> 3 someone else
Created on 2022-10-20 by the reprex package (v2.0.1)

Answer 1

This is what I figured out.
But this is just developing an understanding of the answer at
https://stackoverflow.com/a/51415101/4629916
from #cameron
and applying it to my problem.
tidyr::tibble(myname = c("HarlanNelson", "Another Person", "someone else")) |>
tidyr::separate(col = myname, into = c("first", "last"), sep = "(?<=[[:lower:]])(?=[[:upper:]])", extra = 'merge', fill = 'right') |>
tidyr::separate(col = first, into = c("first", "last2"), sep = " ", fill = 'right', extra = 'merge') |>
dplyr::mutate(last = dplyr::coalesce(last, last2)) |>
dplyr::select(-last2)
#> # A tibble: 3 × 2
#> first last
#> <chr> <chr>
#> 1 Harlan Nelson
#> 2 Another Person
#> 3 someone else
tidyr::tibble(myname = c("HarlanNelson", "Another Person", "someone else")) |>
tidyr::separate(col = myname, into = c("first", "last"), sep = "(?<!^)(?=[[:upper:]])", extra = 'merge', fill = 'right') |>
tidyr::separate(col = first, into = c("first", "last2"), sep = " ", extra = 'merge', fill = 'right') |>
dplyr::mutate(last = dplyr::coalesce(last, last2)) |>
dplyr::select(-last2)
#> # A tibble: 3 × 2
#> first last
#> <chr> <chr>
#> 1 Harlan Nelson
#> 2 Another Person
#> 3 someone else