r - 根据其他列计算列中的总数 - R

Question

如何转换数据框？

之前:

set.seed(1)
df <- data.frame( n = rpois(16, 2),
                  year = rep(2011, 16),
                  month = rep(seq(1,4,1), times = rep(4,4)))

之后:

df1 <- data.frame( n = c(8,11,4,9),
                  year = rep(2011, 4),
                  month = rep(seq(1,4,1)))

Answer 1

我想你想要的是这个，使用dplyr:

library(dplyr)
df %>% 
  group_by(year, month) %>% 
  summarise(n = sum(n))
# A tibble: 4 x 3
# Groups:   year [1]
   year month     n
  <dbl> <dbl> <int>
1  2011     1     8
2  2011     2    11
3  2011     3     4
4  2011     4     9