Re: [R] Identifying unique pairs

From: Vincy Pyne <vincy_pyne_at_yahoo.ca>
Date: Sat, 12 Mar 2011 04:22:53 -0800 (PST)


Thanks sir for your reply. Unfortunately I couldn't figure out the solution.

Vincy

From: Dennis Murphy <djmuser_at_gmail.com>
Subject: Re: [R] Identifying unique pairs To: "Vincy Pyne" <vincy_pyne_at_yahoo.ca>
Cc: r-help_at_r-project.org
Received: Saturday, March 12, 2011, 11:45 AM

Hi:

This problem came up the other day - see

http://stats.stackexchange.com/questions/7884/fast-ways-in-r-to-get-the-first-row-of-a-data-frame-grouped-by-an-identifier/7985#7985

Dennis

On Sat, Mar 12, 2011 at 3:20 AM, Vincy Pyne <vincy_pyne_at_yahoo.ca> wrote:

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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