MAtrix addressing

The reason is the following image
http://img545.imageshack.us/i/maptoregion.jpg/
In the picture above you will find the indexes for each cell.

Also you will see that I place that matrix inside a x,y region that  
spans from -1 to 1. I am trying to write one function that will get  
as argument a (x,y) value x e[-1,1] y e[-1,1] and will return the  
indexes of that cell tha x,y value correspond to.

I really do not have a clue how I should try to approach that to  
solve it. So based on some version I had for 1-d vector I tried to  
extend it for 2-d. I used findInterval as a core to get results.
Unfortunately my code fails to produce accurate results as my  
approach 'assumes' (this is something inhereted by the find Interval  
function) that the numbering starts bottom left and goes high top  
right.
You will find my code below

sr.map <- function(sr){
# This function converts the s(x,y) matrix into a function x that  
spans #from -1 to 1 and y spans from -1 to 1.
# Input: sr a x,y matrix containing the shadowing values of a Region
    breaksX <- seq(from=-1, to = 1, length = nrow(sr) +1L )
    breaksY <- seq(from=-1, to = 1, length = ncol(sr) + 1L)
    function(x,y){ # SPAGGETI CODE FOR EVER
        indx <- findInterval(x, breaksX,rightmost.closed=TRUE)
	 indy <- findInterval(y, breaksY,rightmost.closed=TRUE)
	 c(indx,indy)
    }
}



sr<-matrix(data=seq(from=1,to=36),nrow=6,ncol=6,byrow=TRUE)
f.sr.map<-sr.map((sr))
f.sr.map(-0.1,-0.1)
f.sr.map(0.1,0.1)



Best Regards
Alex





--- On Wed, 1/26/11, David Winsemius <dwinsemius at comcast.net> wrote:

From: David Winsemius <dwinsemius at comcast.net>
Subject: Re: [R] MAtrix addressing
To: "Alaios" <alaios at yahoo.com>
Cc: R-help at r-project.org
Date: Wednesday, January 26, 2011, 2:54 AM

On Jan 25, 2011, at 4:50 PM, Alaios wrote:

Hello
I would like to ask you if it is possible In R Cran to

change the default way of addressing a matrix.

for example
matrix(data=seq(from=1,to=4,nrow=2,ncol=2, by row

numbering) # not having R at this pc

will create something like the following
1 2
3 4

the way R address this matrix is from top left corner

moving to bottom right.

The cell numbers in that way are
1 2
3 4

IS it possible to change this default addresing number

to something that goes bottom left to top right? In this
simple case I want to have

3 4
1 2

Would that be possible?

Yes. it's possible but ... why?

I would like to thank y for your help
Regards
Alex

mailing list

reproducible code.

David Winsemius, MD
West Hartford, CT