ddply for sum by group in R

Question

I have a sample dataframe \"data\" as follows:

X            Y  Month   Year    income
2281205 228120  3   2011    1000
2281212 228121  9   2010    1100
22812         


        

Answer 1

I think the package dplyr is faster than plyr::ddply and more elegant.

testData <- read.table(file = "clipboard",header = TRUE)
require(dplyr)
testData %>%
  group_by(Y) %>%
  summarise(total = sum(income),freq = n()) %>%
  filter(freq > 3)