Yes, in your formula
, you can cbind
the numeric variables to be aggregated:
aggregate(cbind(x1, x2) ~ year + month, data = df1, sum, na.rm = TRUE)
year month x1 x2
1 2000 1 7.862002 -7.469298
2 2001 1 276.758209 474.384252
3 2000 2 13.122369 -128.122613
...
23 2000 12 63.436507 449.794454
24 2001 12 999.472226 922.726589
See ?aggregate
, the formula
argument and the examples.