Question

I have a data set (test)

v1 v2  v3  v4  v5  v6
1   1   1   0   0   0 
2   2   1   1   0   0 
3   2   1   0   0   0 
4   3   1   0   0   0 
5   3   1   1   0   1 
6   3   1   0   1   1 

structure(list(V1 = 1:6, V2 = c(1L, 2L, 2L, 3L, 3L, 3L), V3 = c(1L, 
1L, 1L, 1L, 1L, 1L), V4 = c(0L, 1L, 0L, 0L, 1L, 0L), V5 = c(0L, 
0L, 0L, 0L, 0L, 1L), V6 = c(0L, 0L, 0L, 0L, 1L, 1L)), .Names = c("V1", 
"V2", "V3", "V4", "V5", "V6"), class = "data.frame", row.names = c(NA, 
-6L))

and I want to achieve this

v1  v2  v3  v4  v5  v6
 1   1   1   0   0   0  
 5   2   2   1   0   0  
15   3   3   1   1   2  

I have tried this:

aggregate(test[c('v3', 'v4', 'v5','v6')], list('v2'), FUN=sum, na.rm=TRUE)

which is not working. I want to aggregate the data in (test) based on V2 and sum the other variables.

Answer 1

Change your aggregate command to:

aggregate(. ~ V2, test, sum)
#   V2 V1 V3 V4 V5 V6
# 1  1  1  1  0  0  0
# 2  2  5  2  1  0  0
# 3  3 15  3  1  1  2

Some things to note:

1. R is case sensitive. The sample data you provided has variables named with upper-case “V”s, but the sample code you’ve tried has lower-case “v”s.
2. You’re trying to refer to the variable names directly. For that, you either need to be using the formula notation for aggregate() or you need to be using with() or (not recommended) attach().