[R] Identifying unique pairs

From: Vincy Pyne <vincy_pyne_at_yahoo.ca>
Date: Sat, 12 Mar 2011 03:20:01 -0800 (PST)


Dear R helpers

Suppose I have a data frame as given below

mydat = data.frame(x = c(1,1,1, 2, 2, 2, 2, 2, 5, 5, 6), y = c(10, 10, 10, 8, 8, 8, 7, 7, 2, 2, 4))

mydat

        x     y
1      1     10
2      1     10
3      1     10
4      2       8
5      2       8
6      2       8
7      2       7
8      2       7
9      5       2

10    5       2
11    6       4

unique(mydat$x) will give me 1, 2, 5, 6  i.e. 4 values and unique(mydat$y) will give me 10, 8, 7, 2, 4.

What I need is a data frame where I will get a vector (say) x_new as (1, 2, 2, 5, 6) and corresponding y_new as (10, 8, 7, 2, 4). I need to use these two vectors viz. x_new and y_new seperately for further processing. They may be under same data frame say mydat_new but I should be able to access them as mydat_new$x_new and similarly for y.

I tried following way.

pp = paste(mydat$x, mydat$y)

pp = > pp
 [1] "1 10" "1 10" "1 10" "2 8"  "2 8"  "2 8"  "2 7"  "2 7"  "5 2"  "5 2"  "6 4"

qq = unique(pp)

> qq

[1] "1 10" "2 8"  "2 7"  "5 2"  "6 4"

So I get the desired pairs, but I want each element of pair in two columns seperately as

x_new     y_new

1            10
2              8
2              7
5              2
6              4

Kindly guide

Vincy

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