Conditionally Count in dplyr

Question

I have some member order data that I would like to aggregate by week of order.

This is what the data looks like:

memberorders=data.frame(MemID=c(\'A\         


        

Answer 1

Using the plyr package one could do

ddply(memberorders,.(MemID),
                    summarise, 
                    val1 = sum(value[week<=2]), 
                    val2 = sum(value[week<=4]),
                    val3 = length(value[week<=2]),
                    val4 = length(value[week<=4]))

  MemID val1 val2 val3 val4
1     A   30   30    2    2
2     B   10   20    1    2
3     C    5   35    1    2
4     D    3    3    1    1