[R] simple "for loop" program for merging datasets?

[David Winsemius]

You say you want to merge the two datasets on Country but the last  
step in you unsuccessful effort tries to match the results of the  
nested loop  (necessarily with values of Measure2 from B) to B which  
has 3 rows. You never told us what the final results of this effort  
should be. but surely it is not matching Measure2 up with elements in B.

(Also notice that Country_A[j]= =(Country_B[i] could not possibly do  
anything useful due to the space between the two equal signs.)

Try again to construct a sensible question, copy the results from your  
efforts, and someone will take a stab at offering help.

I suggest you offer dput(A) and dput(B) so we can see whether the  
colnames really have spaces in them.

-- 
David Winsemius


On Mar 19, 2009, at 5:35 PM, J S wrote:

>
> Dear R community,
>
> I would like to merge two datasets based on the categorical  
> predictor “country”.
>
> Dataset A:
>
> Country           Measure1
> Afganistan        1
> Afganistan        1
> Russia              5
> Poland 3
> Poland              2
>
> Dataset B:
>
> Country           Measure 2
> Russia              2
> Afganistan        10
> Poland              15
>
> My program does not work:
>
> Country_A<-A$Country
> Country_B<-B$Country
> Measure2<-B$Measure2
>
> for(i in 1:nrow(B)){
> for(j in 1:nrow(A){
> w[j]<-ifelse(Country_A[j]= =(Country_B[i]),Measure2[i], NA)
> }}
>
> A2<-cbind(B,w)
>
>
> Thanks, Julia
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT