Using pivot_longer to turn multiple columns into one in R [duplicate]

Answer 1

Here a solution that makes use of num_range for tidy selection of the columns before the call to pivot_longer:

library(dplyr)
library(tidyr)

df_long <- df %>% 
  select(Region, num_range("X", 1975:1999)) %>% 
  pivot_longer(-Region,
               names_to = "Year",
               names_prefix = "X",
               values_to = "Population")

> df_long
# A tibble: 850 x 3
   Region         Year  Population
                   
 1 National Total 1975       92420
 2 National Total 1976       93717
 3 National Total 1977       94974
 4 National Total 1978       96259
 5 National Total 1979       97542
 6 National Total 1980       98705
 7 National Total 1981      100072
 8 National Total 1982      101654
 9 National Total 1983      103008
10 National Total 1984      104357
# ... with 840 more rows