Expand ranges defined by “from” and “to” columns

Question

I have a data frame containing \"name\" of U.S. Presidents, the years when they start and end in office, (\"from\" and \"to\" columns

Answer 1

An alternate tidyverse approach using unnest and map2.

library(tidyverse)

presidents %>%
  unnest(year = map2(from, to, seq)) %>%
  select(-from, -to)

#              name  year
# 1    Bill Clinton  1993
# 2    Bill Clinton  1994
...
# 21   Barack Obama  2011
# 22   Barack Obama  2012

Edit: From tidyr v1.0.0 new variables can no longer be created as part of unnest().

presidents %>%
  mutate(year = map2(from, to, seq)) %>%
  unnest(year) %>%
  select(-from, -to)