Counting unique pairs of categorical variables in R [duplicate]

Answer 1

table(as.character(interaction(df)))

Or

library(qdap)
table(paste2(df))

# X.A X.B Y.B Z.B Z.C 
#   2   2   3   1   1 

Answer 2

This is the dplyr solution.

library(dplyr)

df %>% group_by(One,Two) %>%
      summarize(Count = n())

This returns a data frame like this

Source: local data frame [5 x 3]
Groups: One

  One Two Count
1   X   A     2
2   X   B     2
3   Y   B     3
4   Z   B     1
5   Z   C     1