How do I convert the dataframe?
Before:
set.seed(1)
df <- data.frame( n = rpois(16, 2),
year = rep(2011, 16),
month = rep(seq(1,4,1), times = rep(4,4)))
After:
df1 <- data.frame( n = c(8,11,4,9),
year = rep(2011, 4),
month = rep(seq(1,4,1)))
I think that what you want is this, using 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
Using base R with aggregate
aggregate(n ~ ., df, sum)
# year month n
#1 2011 1 8
#2 2011 2 11
#3 2011 3 4
#4 2011 4 9