Frequency count of two column in R

Question

I have two columns in data frame

2010  1
2010  1
2010  2
2010  2
2010  3
2011  1
2011  2

I want to count frequency of both columns and get the result in this format

  y    m Freq
 2010  1 2
 2010  2 2
 2010  3 1
 2011  1 1
 2011  2 1 

Answer 1

If your data is dataframe df with columns y and m

library(plyr)
counts <- ddply(df, .(df$y, df$m), nrow)
names(counts) <- c("y", "m", "Freq")