split a column in two existing columns if a condition is matched in R

I have a df like this:

df <- data.frame(id=c("j1", "j2", "j3/j9", "j5", "j2/j8", "j3/j4"), dad=c("j10", "j11", "", "j13", "", ""), mom=c("k2", "k4", "", "k6", "", ""))

I am trying to split only those cells that contain a slash "/" in the column "id". I want to get the split string in the existing columns "dad" and "mom". The desired output would be this:

df2 <- data.frame(id=c("j1", "j2", "j3/j9", "j5", "j2/j8", "j3/j4"), dad=c("j10", "j11", "j3", "j13", "j2", "j3"), mom=c("k2", "k4", "j9", "k6", "j8", "j4"))

I am trying this code:

df3 <- tidyr::separate(data = df, col = "id", into = c("dad", "mom"), sep = "/")

but that split the entire column "id" in two new columns. Any idea how to solve this?

>Solution :

You could use:

library(dplyr)
library(stringr)

df %>% 
  mutate(dad = if_else(str_detect(id, "/"), str_extract(id, ".*(?=/)"), dad),
         mom = if_else(str_detect(id, "/"), str_extract(id, "(?<=/).*"), mom))

This returns

     id dad mom
1    j1 j10  k2
2    j2 j11  k4
3 j3/j9  j3  j9
4    j5 j13  k6
5 j2/j8  j2  j8
6 j3/j4  j3  j4