Creating new variable by focusing range of other variables

Question

I want to create a variable that include all numbers between (startyear) and (endyear - 1). My data looks like this:

country	leader	startyear	endyear
US	Eisenhower	1953	1961
US	Kennedy	1961	1963

I want to show my data like this:

country	leader	startyear	endyear	year
US	Eisenhower	1953	1961	1953
US	Eisenhower	1953	1961	1954
US	Eisenhower	1953	1961	1955
US	Eisenhower	1953	1961	1956
US	Eisenhower	1953	1961	1957
US	Eisenhower	1953	1961	1958
US	Eisenhower	1953	1961	1959
US	Eisenhower	1953	1961	1960
US	Kennedy	1961	1963	1961
US	Kennedy	1961	1963	1962

I have many countries in data set. I want to manipulate all data set with "the" code.

Answer 1

We may get the sequence (:) by row and unnest the list column

library(dplyr)
library(purrr)
library(tidyr)
df1 %>%
   mutate(year = map2(startyear, endyear-1, `:`)) %>%
   unnest(year)

-output

# A tibble: 10 × 5
   country leader     startyear endyear  year
   <chr>   <chr>          <int>   <int> <int>
 1 US      Eisenhower      1953    1961  1953
 2 US      Eisenhower      1953    1961  1954
 3 US      Eisenhower      1953    1961  1955
 4 US      Eisenhower      1953    1961  1956
 5 US      Eisenhower      1953    1961  1957
 6 US      Eisenhower      1953    1961  1958
 7 US      Eisenhower      1953    1961  1959
 8 US      Eisenhower      1953    1961  1960
 9 US      Kennedy         1961    1963  1961
10 US      Kennedy         1961    1963  1962

data

df1 <- structure(list(country = c("US", "US"), leader = c("Eisenhower", 
"Kennedy"), startyear = c(1953L, 1961L), endyear = c(1961L, 1963L
)), class = "data.frame", row.names = c(NA, -2L))