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

Here is a solution using the plyr package

plyr::ddply(df, .(A), summarize, num = length(A), totalB = sum(B))