[R] R version 3.3.2, Windows 10: Applying a function to each possible pair of rows from two different data-frames

[Bert Gunter]

You appear to be trying to write C code in R. Don't do this. If you
can trade off space for efficiency, the calculation can be easily
vectorized (assuming I correctly understand what you want to do, of
course).

set.seed(135) ## for reproducibility
D1<-data.frame(x=1:5,y=6:10,z=rnorm(5))
D2<-data.frame(x=19:30,y=41:52,z=rnorm(12))

D.all <-merge(D1,D2, by.x=NULL,by.y=NULL) ## Cartesian product of the two frames

D.all$distance <- sqrt(rowSums((D.all[,1:2] - D.all[,4:5])^2)) ## note
use of rowSums
D.all$difference <- (D.all[,3] - D.all[,6])^2

D.all



Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Fri, Jun 23, 2017 at 8:19 AM, Rathore, Saubhagya Singh
<saubhagya at gatech.edu> wrote:
> For certain reason, the content was not visible in the last mail, so posting it again.
>
> Dear Members,
>
> I have two different dataframes with a different number of rows. I need to apply a set of functions to each possible combination of rows with one row coming from 1st dataframe and other from 2nd dataframe. Though I am able to perform this task using for loops, I feel that there must be a more efficient way to do it. An example case is given below. D1 and D2 are two dataframes. I need to evaluate D3 with one column as the Euclidean distance in the x-y plane and second column as squared difference of z values, of each row pair from D1 and D2.
>
> D1<-data.frame(x=1:5,y=6:10,z=rnorm(5))
> D2<-data.frame(x=19:30,y=41:52,z=rnorm(12))
> D3<-data.frame(distance=integer(0),difference=integer(0))
>
> for (i in 1:nrow(D1)){
>
> for (j in 1:nrow(D2))  {
>
> temp<-data.frame(distance=sqrt(sum((D1[i,1:2]-D2[j,1:2])^2)),difference=(D1[i,3]-D2[j,3])^2)
> D3<-rbind(D3,temp)
> }
> }
>
> Thank you
>
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of r-help-owner at r-project.org
> Sent: Friday, June 23, 2017 10:47 AM
> To: Rathore, Saubhagya Singh <saubhagya at gatech.edu>
> Subject: R version 3.3.2, Windows 10: Applying a function to each possible pair of rows from two different data-frames
>
> The message's content type was not explicitly allowed
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.