[R] Sorted index of values in matrix

[Bert Gunter]

... and here is another version of Jeff's solution using the built in
row() and col() functions instead of explicitly creating the indices
(but his version generalizes to arbitrary arrays; this does not):

 qq <- matrix(12:7, nrow =3) ## start with a non-sorted matrix
> qq
     [,1] [,2]
[1,]   12    9
[2,]   11    8
[3,]   10    7
> sort(qq)
[1]  7  8  9 10 11 12 ## the sorted values

> o <- order(qq)
> cbind(row(qq)[o], col(qq)[o])
## matrix of (row, col) indices of sorted values in original unsorted matrix
     [,1] [,2]
[1,]    3    2
[2,]    2    2
[3,]    1    2
[4,]    3    1
[5,]    2    1
[6,]    1    1

Cheers,
Bert Gunter

On Fri, Apr 15, 2022 at 8:33 AM Jeff Newmiller <jdnewmil using dcn.davis.ca.us> wrote:
>
> Please stop posting in HTML format.
>
> I think your specified result coordinates are in (col,row) order, which is not normal for R. The solution below yields (row,col) order.
>
> qq <- structure(1:6, .Dim = 3:2, .Dimnames = list(c("1", "2", "3"), c("1", "2")))
> pos <- expand.grid( r = seq.int( nrow( qq ) )
>                   , c = seq.int( ncol( qq ) ) )
> qq #'confirm source layout is column major
> pos[ order( qq ), ] # (row,col)
> pos[ order( qq ), 2:1 ] # (col,row)
>
>
> On April 15, 2022 7:53:36 AM PDT, Eliza Botto <eliza_botto using outlook.com> wrote:
> >deaR useRs,
> >
> >I have this following simple dataset
> >
> >> dput(qq)
> >
> >structure(1:6, .Dim = 3:2, .Dimnames = list(c("1", "2", "3"),
> >    c("1", "2")))
> >
> >I want to extract row and column index of the sorted values of this matrix
> >
> >For example,
> >
> >sort(qq) command will execute the sorted values of this matrix as (1 2 3 4 5 6). Instead of values, I want the row and column names of these sorted values as (1,1), (1,2), (1,3), (2,1), (2,2), (2,3)
> >
> >I thankyou very much in advance for your help.
> >
> >Eliza
> >
> >
> >       [[alternative HTML version deleted]]
> >
> >______________________________________________
> >R-help using 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.
>
> --
> Sent from my phone. Please excuse my brevity.
>
> ______________________________________________
> R-help using 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.