-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Hi Steven,
This looks great. Thanks!
Nathan
Steve Lianoglou wrote:
> Hi Nathan,
>
> On Jul 8, 2009, at 10:20 PM, Nathan S. Watson-Haigh wrote:
>
>> I have two matrices:
>>
>>> m1 <- matrix(1,4,4)
>>> m1
>> [,1] [,2] [,3] [,4]
>> [1,] 1 1 1 1
>> [2,] 1 1 1 1
>> [3,] 1 1 1 1
>> [4,] 1 1 1 1
>>
>>> m2 <- matrix(0,3,3)
>>> diag(m2) <- 1
>>> m2
>> [,1] [,2] [,3]
>> [1,] 1 0 0
>> [2,] 0 1 0
>> [3,] 0 0 1
>>
>> I want to get indicies from m2 such that they match indicies as
>> though they came
>> from the lower right of m1. Here's how things work:
>>
>>> ind1 <- which(m1 == 1)
>>> ind1
>> [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
>>> ind2 <- which(m2 == 1)
>>> ind2
>> [1] 1 5 9
>>
>>
>> I would like ind2 to be offset so they look like indicies from the
>> lower right
>> of m1:
>>> ind2
>> [1] 6 11 16
>
>
> I have written some utility functions I use often[1], and have
> "sub2ind" function that works in a similar fashion to the MATLAB
> function of the same name. It's somehow long and convoluted because
> you can send in your arguments 12 different ways from sunday, so:
>
> sub2ind <- function(x, y, nrow, ncol=NULL) {
> ## Returns a linear index for the (x,y) coordinates passed in.
> if (is.matrix(x) || is.data.frame(x)) {
> stopifnot(ncol(x) == 2)
> if (!missing(y)) {
> if (missing(nrow)) {
> nrow <- y
> } else {
> ncol <- nrow
> nrow <- y
> }
> }
> y <- x[,2]
> x <- x[,1]
> }
>
> if (is.matrix(nrow)) {
> d <- dim(nrow)
> nrow <- d[1]
> ncol <- d[2]
> } else if (is.null(ncol)) {
> stop("Dimensions of matrix under-specified")
> }
>
> # Sanity check to ensure we got each var doing what it should be
> doing
> if (length(x) != length(y) || length(nrow) != 1 || length(ncol) !=
> 1) {
> stop("I'm confused")
> }
>
> ((x - 1) + ((y - 1) * nrow)) + 1
>
> }
>
> R> m1 <- matrix(1,4,4)
> R> m2 <- matrix(0,3,3)
> R> ind2 <- which(m2 == 1, arr.ind=T) + 1
> R> ind2
> row col
> [1,] 2 2
> [2,] 3 3
> [3,] 4 4
>
> R> my.ind2 <- sub2ind(ind2, nrow=4, ncol=4)
> # my.ind2 <- sub2ind(ind2[,1], ind2[,2], 4, 4)
> # my.ind2 <- sub2ind(ind2[,1], ind2[,2], m1)
> # my.ind2 <- sub2ind(ind2, m1)
> R> my.ind2
> [1] 6 11 16
>
> I think that gets you to where you want to be :-)
>
> -steve
>
> [1] They can be found here if your intersted, there isn't much
> documentation there, but I'll fix that some time later :-)
> http://github.com/lianos/ARE.utils/tree/master
>
> --
> Steve Lianoglou
> Graduate Student: Physiology, Biophysics and Systems Biology
> Weill Medical College of Cornell University
>
> Contact Info: http://cbio.mskcc.org/~lianos
>
>
>
- --
- --------------------------------------------------------
Dr. Nathan S. Watson-Haigh
OCE Post Doctoral Fellow
CSIRO Livestock Industries
Queensland Bioscience Precinct
St Lucia, QLD 4067
Australia
Tel: +61 (0)7 3214 2922
Fax: +61 (0)7 3214 2900
Web: http://www.csiro.au/people/Nathan.Watson-Haigh.html
- --------------------------------------------------------
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
iEYEARECAAYFAkpWfCQACgkQ9gTv6QYzVL5zQQCffRi6SUNhtrfbMdBKadYSHGVe
00YAni90MgPiUOlBmcEq90FB/Zj/50Hz
=rZ4B
-----END PGP SIGNATURE-----
______________________________________________
R-help@r-project.org 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.
