[R] Randomly selecting rows with unique values in two columns

[David Winsemius]

On Sep 26, 2011, at 5:42 PM, hasan wrote:

> Hello,
>
> I am trying to randomly select rows with unique values in columns 1  
> and 2. I
> want to generate multiple subsets to estimate a statistic for each  
> data set.
> Below is a simplified example.
>
>   L1 L2 L3 L4 L5
> 1   a  b  1  2  3
> 2   a  c  4  5  6
> 3   a  d  7  8  9
> 4   a  e 10 11 12
> 5   a  f 13 14 15
> 6   b  c 16 17 18
> 7   b  d 19 20 21
> 8   b  e 22 23 24
> 9   b  f 25 26 27
> 10  c  d 28 29 30
> 11  c  e 31 32 33
> 12  c  f 34 35 36
> 13  d  e 37 38 39
> 14  d  f 40 41 42
> 15  e  f 43 44 45

I think this is isomorphic to a question in the last couple of days on  
StackOverflow:

http://stackoverflow.com/questions/7536218/how-do-i-take-subsets-of-a-data-frame-according-to-a-grouping-in-r-tricky-aggre/7536610#7536610

(I don't think the -1 score on my tapply solution is exactly fair. but  
I suspect that Ari has moved on to other things and is not going back  
to check up on edits. I think w=either solution should provide a  
random selection within groups.)


>
> Could you please give directions to where to start? I have tried  
> eliminating
> duplicates and finding unique rows but no successful to make it  
> random.
>
> Thanks
>
> Hasan
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Randomly-selecting-rows-with-unique-values-in-two-columns-tp3845504p3845504.html
> Sent from the R help mailing list archive at Nabble.com.
>
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David Winsemius, MD
West Hartford, CT