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

Here's a dplyr solution:

library(dplyr)

# the data
presidents <- 
structure(list(name = c("Bill Clinton", "George W. Bush", "Barack Obama"
), from = c(1993, 2001, 2009), to = c(2001, 2009, 2012)), .Names = c("name", 
"from", "to"), row.names = 42:44, class = "data.frame")

# the expansion of the table
presidents %>%
    rowwise() %>%
    do(data.frame(name = .$name, year = seq(.$from, .$to, by = 1)))

# the output
Source: local data frame [22 x 2]
Groups: 

             name  year
            (chr) (dbl)
1    Bill Clinton  1993
2    Bill Clinton  1994
3    Bill Clinton  1995
4    Bill Clinton  1996
5    Bill Clinton  1997
6    Bill Clinton  1998
7    Bill Clinton  1999
8    Bill Clinton  2000
9    Bill Clinton  2001
10 George W. Bush  2001
..            ...   ...

h/t: https://stackoverflow.com/a/24804470/1036500