[R] unique, but keep LAST occurence

[davidr at rhotrading.com]

Thank you, Bert and Mark.
I believe Mark's solution works, but it was taking a very long time.
Bert's is very fast.

My day is saved!

David L. Reiner
Rho Trading Securities, LLC
Chicago  IL  60605
312-362-4963

-----Original Message-----
From: Berton Gunter [mailto:gunter.berton at gene.com] 
Sent: Monday, July 24, 2006 12:51 PM
To: David Reiner <davidr at rhotrading.com>; r-help at stat.math.ethz.ch
Subject: RE: [R] unique, but keep LAST occurence

Try:

 largestDF <- DF[nrow(DF)- which(!duplicated(rev(DF$t)))+1,]

You can then sort this however you like in the usual way. Row names will be
preserved.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> davidr at rhotrading.com
> Sent: Monday, July 24, 2006 10:00 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] unique, but keep LAST occurence
> 
> ?unique says
> 
> Value:
> 
>      An object of the same type of 'x'. but if an element is equal to
>      one with a smaller index, it is removed.
> 
> However, I need to keep the one with the LARGEST index.
> Can someone please show me the light? 
> I thought about reversing the row order twice, but I couldn't 
> get it to work right
> 
> (My data frame has 125000 rows and 7 columns, 
> and I'm 'uniqueing' on column #1 (chron) only, although the 
> class of the column may not matter.)
> 
> Say, e.g., 
> > DF <- data.frame(t = c(1,2,3,1,4,5,1,2,3), x = c(0,1,2,3,4,5,6,7,8))
> 
> I would like the result to be (sorted as well)
>  t x
>  1 6
>  2 7
>  3 8
>  4 4
>  5 5
> 
> If I got the original rownames, that would be a bonus (for debugging.)
> 
> > R.version
>                _                         
> platform       i386-pc-mingw32           
> arch           i386                      
> os             mingw32                   
> system         i386, mingw32             
> status                                   
> major          2                         
> minor          3.1                       
> year           2006                      
> month          06                        
> day            01                        
> svn rev        38247                     
> language       R                         
> version.string Version 2.3.1 (2006-06-01)
> 
> Thanks for any hints!
> David
> 
> David L. Reiner
> Rho Trading Securities, LLC
> Chicago  IL  60605
> 312-362-4963
> 
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