[SOLVED] Split a string into rows by delimiter and add column with order

Split a string into rows by delimiter and add column with order

I know how to split a string into rows by a delimiter from

V1	V2
1	h,e
2	l,l,o

V1	V2
1	h
1	e
2	l
2	l
2	o

with tidyr::separate_longer_delim(V2, delim = ",") but how can I add a column with the original order of the individual string parts as in

V1	V2	order
1	h	1
1	e	2
2	l	1
2	l	2
2	o	3

Solution

Using purrr::map to get the order variable, then unnest to get the elements per row

library(dplyr)
library(tidyr)

df %>% 
  mutate(V2 = strsplit(V2, ","), 
         order = purrr::map(lengths(V2), ~ seq_len(.x))) %>% 
  unnest(-V1)
# A tibble: 5 × 3
     V1 V2    order
  <int> <chr> <int>
1     1 h         1
2     1 e         2
3     2 l         1
4     2 l         2
5     2 o         3

Data

df <- structure(list(V1 = 1:2, V2 = c("h,e", "l,l,o")), class = "data.frame", 
row.names = c(NA, -2L))