Aggregate data in one column based on values in another column

Question

I know there is an easy way to do this...but, I can\'t figure it out.

I have a dataframe in my R script that looks something like this:

A      B    C
1.2         


        

Answer 1

I'd use aggregate to get the two aggregates and then merge them into a single data frame:

> df
    A B C
1 1.2 4 8
2 2.3 4 9
3 2.3 6 0
4 1.2 3 3
5 3.4 2 1
6 1.2 5 1

> num <- aggregate(B~A,df,length)
> names(num)[2] <- 'num'

> totalB <- aggregate(B~A,df,sum)
> names(totalB)[2] <- 'totalB'

> merge(num,totalB)
    A num totalB
1 1.2   3     12
2 2.3   2     10
3 3.4   1      2