[R] Updating a data frame

David Winsemius dwinsemius at comcast.net
Fri Apr 3 02:21:16 CEST 2009


I am sure this is not the most elegant method, but it will "work".

 > new <- merge(nn,uu, by = c("a","b"), all.x=T)

 > new
    a b        x.x        y.x x.y  y.y
1  1 1 0.03648491 0.69644753 100 -100
2  1 2 0.76826365 0.28821953  NA   NA
3  1 3 0.62744363 0.08373154  NA   NA
4  2 1 0.27503185 0.55738251  NA   NA
5  2 2 0.45890263 0.80790679 200 -100
6  2 3 0.19193329 0.88803516  NA   NA
7  3 1 0.36065586 0.72215405  NA   NA
8  3 2 0.93962690 0.10943878  NA   NA
9  3 3 0.68443490 0.06951730 300 -100
10 4 1 0.52525832 0.29631353 400 -100
11 4 2 0.56332173 0.63063714  NA   NA
12 4 3 0.37129221 0.40779830  NA   NA
 > new$y <- with( new, (ifelse(!is.na(x.y), y.y, y.x) )  )
 > new
    a b        x.x        y.x x.y  y.y             y
1  1 1 0.03648491 0.69644753 100 -100 -100.00000000
2  1 2 0.76826365 0.28821953  NA   NA    0.28821953
3  1 3 0.62744363 0.08373154  NA   NA    0.08373154
4  2 1 0.27503185 0.55738251  NA   NA    0.55738251
5  2 2 0.45890263 0.80790679 200 -100 -100.00000000
6  2 3 0.19193329 0.88803516  NA   NA    0.88803516
7  3 1 0.36065586 0.72215405  NA   NA    0.72215405
8  3 2 0.93962690 0.10943878  NA   NA    0.10943878
9  3 3 0.68443490 0.06951730 300 -100 -100.00000000
10 4 1 0.52525832 0.29631353 400 -100 -100.00000000
11 4 2 0.56332173 0.63063714  NA   NA    0.63063714
12 4 3 0.37129221 0.40779830  NA   NA    0.40779830
 > new$x <- with( new, (ifelse(!is.na(x.y), x.y, x.x) ) )
 > new
    a b        x.x        y.x x.y  y.y             y           x
1  1 1 0.03648491 0.69644753 100 -100 -100.00000000 100.0000000
2  1 2 0.76826365 0.28821953  NA   NA    0.28821953   0.7682636
3  1 3 0.62744363 0.08373154  NA   NA    0.08373154   0.6274436
4  2 1 0.27503185 0.55738251  NA   NA    0.55738251   0.2750319
5  2 2 0.45890263 0.80790679 200 -100 -100.00000000 200.0000000
6  2 3 0.19193329 0.88803516  NA   NA    0.88803516   0.1919333
7  3 1 0.36065586 0.72215405  NA   NA    0.72215405   0.3606559
8  3 2 0.93962690 0.10943878  NA   NA    0.10943878   0.9396269
9  3 3 0.68443490 0.06951730 300 -100 -100.00000000 300.0000000
10 4 1 0.52525832 0.29631353 400 -100 -100.00000000 400.0000000
11 4 2 0.56332173 0.63063714  NA   NA    0.63063714   0.5633217
12 4 3 0.37129221 0.40779830  NA   NA    0.40779830   0.3712922

 > new[ , c("a", "b", "x", "y")]
    a b           x             y
1  1 1 100.0000000 -100.00000000
2  1 2   0.7682636    0.28821953
3  1 3   0.6274436    0.08373154
4  2 1   0.2750319    0.55738251
5  2 2 200.0000000 -100.00000000
6  2 3   0.1919333    0.88803516
7  3 1   0.3606559    0.72215405
8  3 2   0.9396269    0.10943878
9  3 3 300.0000000 -100.00000000
10 4 1 400.0000000 -100.00000000
11 4 2   0.5633217    0.63063714
12 4 3   0.3712922    0.40779830

--  
David Winsemius

On Apr 2, 2009, at 7:09 PM, Seeliger.Curt at epamail.epa.gov wrote:

> Folks,
>
> Updating values in a table is simple in SAS or SQL, but I've wracked  
> my
> brain looking for an elegant solution in R to no avail thus far.  
> Certainly
> this is a common need that's been solved in dozens of different ways.
>
> Given an initial dataframe nn and a smaller dataframe of updates uu,  
> I'd
> like to replace the values in
> nn <- expand.grid('a'=1:4, 'b'=1:3)
> nn$x <- runif(nrow(nn))
> nn$y <- runif(nrow(nn))
> uu <- rbind(data.frame('a'=1, 'b'=1, 'x'=100, 'y'=-100)
>           ,data.frame('a'=2, 'b'=2, 'x'=200, 'y'=-100)
>           ,data.frame('a'=4, 'b'=1, 'x'=400, 'y'=-100)
>           ,data.frame('a'=3, 'b'=3, 'x'=300, 'y'=-100)
>           )
>
> I'd like the result <- f(nn, uu) to look like
>   a b         x         y
> 1  1 1 100       -100
> 2  2 1 0.8310890 0.2516533
> 3  3 1 0.4304501 0.3004313
> 4  4 1 400       -100
> 5  1 2 0.9546661 0.2935739
> 6  2 2 200       -100
> 7  3 2 0.6941463 0.9356967
> 8  4 2 0.9642832 0.9253482
> 9  1 3 0.8735154 0.6055080
> 10 2 3 0.6665369 0.2938112
> 11 3 3 300       -100
> 12 4 3 0.7268327 0.4536969
>
> Anyone spare a clue about what f() might look like?
> Thanks,
> cur
>
> -- 
> Curt Seeliger, Data Ranger
> Raytheon Information Services - Contractor to ORD
> seeliger.curt at epa.gov
> 541/754-4638
>
> 	[[alternative HTML version deleted]]
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT



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