如何在将年份设置为单独值的数据集中对十年进行的观察进行分组和计数？

Question

I have the folllowing dataset:

# A tibble: 90 × 2
   decade     n
    <dbl> <int>
 1   1930    13
 2   1931    48
 3   1932    44
 4   1933    76
 5   1934    73
 6   1935    63
 7   1936    54
 8   1937    51
 9   1938    41
10   1939    42
# … with 80 more rows

With more years that continue until 2010. I wish to "group" by decade like 1930s, 1940s, etc... and to have on another column the count of n in each year until the end of the decade.

For example:

# A tibble: 90 × 2
   decade     n
    <dbl>        <int>
 1   1930-1939    449
 2   1940-1949    516 

Thanks!

Answer 1

We could use the modulo operator %% :

library(dplyr)

df %>% 
  group_by(decade = decade - decade %% 10) %>% 
  summarise(n = sum(n))

  decade     n
   <dbl> <int>
1   1930   505