[S] frequency of data points

[Kin Cheung <kin_cheung@alkermes.com>]

Dear S+ users,

        I need to create vector in a data frame indicating the
number of frequency data points. For example,

x_c(9,1,2,4,5,9,1,2,6,2,7)
y_c(9,1,2,3,5,9,1,2,4,2,8)
xy_cbind(x,y)

> xy
      x y 
 [1,] 9 9
 [2,] 1 1
 [3,] 2 2
 [4,] 4 3
 [5,] 5 5
 [6,] 9 9
 [7,] 1 1
 [8,] 2 2
 [9,] 6 4
[10,] 2 2
[11,] 7 8


The output that I need would be

> xy
      x y z
 [1,] 9 9 2
 [2,] 1 1 2
 [3,] 2 2 3
 [4,] 4 3 1
 [5,] 5 5 1
 [6,] 9 9 2
 [7,] 1 1 2
 [8,] 2 2 3
 [9,] 6 4 1
[10,] 2 2 3
[11,] 7 8 1

The new vector Z is the number of occurrence of the data points X and Y.

Any help from anyone would be great appreciated.

--cheung







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