R help - May 2007 - how to get column/row info from a dist object?

Dear R users;

Is it possible to get the row and column number of a particular entry
in a dist object?

Let's say that I want to find the position of the value 1.1837 (the
last entry on the dist object below), that is [6,3]. Can I get those
values without transforming the object to a matrix?, i.e. working with
the dist object only.

            1                2               3
2  0.23935864
3  0.56655914 0.71923104
4  0.15272561 0.37926989 0.43931332
5  0.17728654 0.13355685 0.73025495
6  0.61783536 0.52055379 1.18374889

Thanks for any idea
PM

But the dist object is not structured with rows and columns.  i.e.

x=1:4

d=dist(x)
   1 2 3
2 1
3 2 1
4 3 2 1

str(d)
Class 'dist'  atomic [1:6] 1 2 3 1 2 1
   ..- attr(*, "Size")= int 4
   ..- attr(*, "Diag")= logi FALSE
   ..- attr(*, "Upper")= logi FALSE
   ..- attr(*, "method")= chr "euclidean"
   ..- attr(*, "call")= language dist(x = x)

So, AFAIK if you want to get references for rows and columns you need to 
make it an object that indeed has rows and columns, i.e. a matrix.  See 
?which to obtain the reference you want in a matrix.

Regards,

Francisco


Pedro Mardones wrote:
> Dear R users;
> 
> Is it possible to get the row and column number of a particular entry
> in a dist object?
> 
> Let's say that I want to find the position of the value 1.1837 (the
> last entry on the dist object below), that is [6,3]. Can I get those
> values without transforming the object to a matrix?, i.e. working with
> the dist object only.
> 
>             1                2               3
> 2  0.23935864
> 3  0.56655914 0.71923104
> 4  0.15272561 0.37926989 0.43931332
> 5  0.17728654 0.13355685 0.73025495
> 6  0.61783536 0.52055379 1.18374889
> 
> Thanks for any idea
> PM
> 
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.
>

which(..., arr.ind=TRUE)

On 5/11/07, Pedro Mardones <mardones.p at gmail.com>
wrote:
> Dear R users;
>
> Is it possible to get the row and column number of a particular entry
> in a dist object?
>
> Let's say that I want to find the position of the value 1.1837 (the
> last entry on the dist object below), that is [6,3]. Can I get those
> values without transforming the object to a matrix?, i.e. working with
> the dist object only.
>
>            1                2               3
> 2  0.23935864
> 3  0.56655914 0.71923104
> 4  0.15272561 0.37926989 0.43931332
> 5  0.17728654 0.13355685 0.73025495
> 6  0.61783536 0.52055379 1.18374889
>
> Thanks for any idea
> PM
>
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

On 5/11/07, Pedro Mardones <mardones.p at gmail.com>
wrote:
> Dear R users;
>
> Is it possible to get the row and column number of a particular entry
> in a dist object?
>
> Let's say that I want to find the position of the value 1.1837 (the
> last entry on the dist object below), that is [6,3]. Can I get those
> values without transforming the object to a matrix?, i.e. working with
> the dist object only.
>
>            1                2               3
> 2  0.23935864
> 3  0.56655914 0.71923104
> 4  0.15272561 0.37926989 0.43931332
> 5  0.17728654 0.13355685 0.73025495
> 6  0.61783536 0.52055379 1.18374889
>
> Thanks for any idea
> PM
Try this.

row.col <- function(dd, value) {
	if (length(value) == 1) {
		g <- grep(value, dd)
		N <- attr(dd, "Size")
		idx <- cumsum(seq(N-1, 1))
		ic <- sum(g > idx) + 1
		ir <- g - c(0,idx)[ic] + ic
		c(row = ir, col = ic)
	} else sapply(value, row.col, dd = dd)
}

# test
set.seed(1)
x <- matrix(rnorm(100), nrow=5)
dd <- dist(x)
dd
dd[7]
row.col(dd, dd[7])
row.col(dd, unlist(dd))