melt + strsplit, or opposite to aggregate

Question

I have a little question that seems to be so easy in concept, but I cannot find the way to do it...

Say I have a data.frame df2 with a column listing car brands and anot

Answer 1

These days I would use tidytext::unnest_tokens for this task:

library(tidytext)
df2 %>% 
  unnest_tokens(model, models, token = "regex", pattern = ",")

# A tibble: 10 x 2
    brand model
    
 1      a    a1
 2      a    a2
 3      a    a3
 4      b    b1
 5      b    b2
 6      c    c1
 7      d    d1
 8      d    d2
 9      d    d3
10      d    d4