R help - Feb 2013 - Merging and Updating Data Frames with Unequal Size

Dear All,
I am trying to merge 2 dataframes of with different sizes.
Let's say that one dataframe R contains some raw data and another data  
frame F contains the information to fix R.
For instance

F <- data.frame(cbind(x=-seq(10),
                       y=1:10,
                       z=3:12,
                       w=8:17,
                       p=18
                       ))



R <- data.frame(cbind(x=rep(-seq(3),5), y=18:32,z=100:86,w=4,k=9))

I would like to do the following: for every value of R$x (i.e. 1,2,3 in  
this case), I will look up the same value in
F$x and use the info on that row of F to update the values of R$y, R$z,R$w  
(i.e. the raws which have the same names in both data frames), whereas I  
will simply append (as a new column) the values of F$p to the new  
dataframe.

The resulting data frame should look like this

  x y z  w k  p
-1 1 3  8 9 18
-2 2 4  9 9 18
-3 3 5 10 9 18
-1 1 3  8 9 18
-2 2 4  9 9 18
-3 3 5 10 9 18
-1 1 3  8 9 18
-2 2 4  9 9 18
-3 3 5 10 9 18
-1 1 3  8 9 18
-2 2 4  9 9 18
-3 3 5 10 9 18
-1 1 3  8 9 18
-2 2 4  9 9 18
-3 3 5 10 9 18

(it took longer to explain it than to do it!).

I can do this with a double loop, but I think that playing with the merge  
command should do the trick, although so far I have been unsuccessful.
Any suggestion is welcome.

Lorenzo

Hi,
Try:
?R[,2:4]<-F[,2:4][match(R$x,F$x),]
?R$p<- unique(F$p)
??? 
R
??? x y z? w k? p
1? -1 1 3? 8 9 18
2? -2 2 4? 9 9 18
3? -3 3 5 10 9 18
4? -1 1 3? 8 9 18
5? -2 2 4? 9 9 18
6? -3 3 5 10 9 18
7? -1 1 3? 8 9 18
8? -2 2 4? 9 9 18
9? -3 3 5 10 9 18
10 -1 1 3? 8 9 18
11 -2 2 4? 9 9 18
12 -3 3 5 10 9 18
13 -1 1 3? 8 9 18
14 -2 2 4? 9 9 18
15 -3 3 5 10 9 18
A.K.




----- Original Message -----
From: Lorenzo Isella <lorenzo.isella at gmail.com>
To: "r-help at stat.math.ethz.ch" <r-help at stat.math.ethz.ch>
Cc: 
Sent: Friday, February 8, 2013 3:57 PM
Subject: [R] Merging and Updating Data Frames with Unequal Size

Dear All,
I am trying to merge 2 dataframes of with different sizes.
Let's say that one dataframe R contains some raw data and another data frame
F contains the information to fix R.
For instance

F <- data.frame(cbind(x=-seq(10),
? ? ? ? ? ? ? ? ? ? ? y=1:10,
? ? ? ? ? ? ? ? ? ? ? z=3:12,
? ? ? ? ? ? ? ? ? ? ? w=8:17,
? ? ? ? ? ? ? ? ? ? ? p=18
? ? ? ? ? ? ? ? ? ? ? ))



R <- data.frame(cbind(x=rep(-seq(3),5), y=18:32,z=100:86,w=4,k=9))

I would like to do the following: for every value of R$x (i.e. 1,2,3 in this
case), I will look up the same value in
F$x and use the info on that row of F to update the values of R$y, R$z,R$w (i.e.
the raws which have the same names in both data frames), whereas I will simply
append (as a new column) the values of F$p to the new dataframe.

The resulting data frame should look like this

x y z? w k? p
-1 1 3? 8 9 18
-2 2 4? 9 9 18
-3 3 5 10 9 18
-1 1 3? 8 9 18
-2 2 4? 9 9 18
-3 3 5 10 9 18
-1 1 3? 8 9 18
-2 2 4? 9 9 18
-3 3 5 10 9 18
-1 1 3? 8 9 18
-2 2 4? 9 9 18
-3 3 5 10 9 18
-1 1 3? 8 9 18
-2 2 4? 9 9 18
-3 3 5 10 9 18

(it took longer to explain it than to do it!).

I can do this with a double loop, but I think that playing with the merge
command should do the trick, although so far I have been unsuccessful.
Any suggestion is welcome.

Lorenzo

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