[R] Compare rows of two matrices

[Dimitris Rizopoulos]

maybe something like this:

which(is.na(y)!=is.na(x), arr.ind=TRUE)

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "TEMPL Matthias" <Matthias.Templ at statistik.gv.at>
To: <r-help at stat.math.ethz.ch>
Sent: Monday, February 21, 2005 3:48 PM
Subject: [R] Compare rows of two matrices


> Hello,
>
> #I have two matrices, eg.:
>
> y <-  matrix( c(20,  NA,  NA,  45,  50,  19,  32, 101,  10,  22, 
> NA,  NA,  80,  49,  61, 190), ncol=4 )
> x <-  matrix( c(20,  NA,  NA,  NA,  50,  19,  32, 101,  10,  22, 
> NA,  NA,  80,  49,  61, 190), ncol=4 )
>
> #Whereas x contains all NA´s from y plus some additional NA´s.
> #I want to find the index of these additional NA´s. I think, there 
> must be a very easy way to do this.
>
> #Here are the indices of NA´s in x and y:
> l1 <- which(is.na(x), arr.ind=TRUE)
> l2 <- which(is.na(y), arr.ind=TRUE)
>
> #> l1
> #     [,1] [,2]
> #[1,]    2    1
> #[2,]    3    1
> #[3,]    4    1
> #[4,]    3    3
> #[5,]    4    3
>
> #> l2
> #     row col
> #[1,]   2   1
> #[2,]   3   1
> #[3,]   3   3
> #[4,]   4   3
>
> #Now I want to find a matrix, which includes the values of l1, 
> without the rows of l2,
> #which has equal entities (the index of the additional NA´S).
> #In this example the result should be row 3 of l1 with the values 4 
> and 1.
> #The following code works, but I think there must be a much more 
> elegant way to do this.
>
> l3 <- l1
> l3 <- cbind( l1, rep(0, nrow(l1)) )
> num <- 1
>
> for( i in 1:nrow(l1) ){
>  for( j in 1:nrow(l2) ){
>    if( l1[i,1] == l2[j,1] & l1[i,2] == l2[j,2]){
>      l3[i,3] <- 1
>    }
>  }
> }
>
> l4 <- l3[l3[,3]==0, c(1,2)]
>
> #> l4
> #row col
> #  4   1
>
> I have often such problems like this and I assume, that other people 
> have similar tasks.
> My question is: Does anybody know a function in one package, which 
> compares rows of two matrices like this or have anybody an idea to 
> do this in a much more elegant way"?
>
> Thank you very much,
> Matthias
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
>