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

by

Here’s a data.table solution. It has the nice (if minor) feature of leaving the presidents in their supplied order:

library(data.table)
dt <- data.table(presidents)
dt[, list(year = seq(from, to)), by = name]
#               name year
#  1:   Bill Clinton 1993
#  2:   Bill Clinton 1994
#  ...
#  ...
# 21:   Barack Obama 2011
# 22:   Barack Obama 2012

Edit: To handle presidents with non-consecutive terms, use this instead:

dt[, list(year = seq(from, to)), by = c("name", "from")]

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