Dear All,
I would like to ask you help with the following:
Assume that I have an area of 36 cells (or sub-areas)
sr<-matrix(data=seq(from=1,to=36),nrow=6,ncol=6,byrow=TRUE)
> sr
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 2 3 4 5 6
[2,] 7 8 9 10 11 12
[3,] 13 14 15 16 17 18
[4,] 19 20 21 22 23 24
[5,] 25 26 27 28 29 30
[6,] 31 32 33 34 35 36
This 6*6 matrix denotes an area and the contents of the cell denote the values
the area gets inside that cell-zone (or sub-area).
I would like to map this AREA into x,y function for x e[-1,1] ye[-1,1]
I really didn't know how to implement that, so with help I got from a list
member I tried to use FindInterval for the x,y plane. I am sure that it might
be an easier way to do that so please do suggest it. If there is not then
continue reading.
In the picture below:
http://img521.imageshack.us/f/maparea.gif/
You can see the matrix presented above placed inside the x e[-1,1] ye[-1,1]
which from now on these are the results of the f(x,y) function.
I.e f(-0.5,0.3) will return the appropriate cell (x,y) index.
As I told you I tried using the findInterval to get for the f(x,y) as an output
the correct cell number.
This is what I have implemented so far (you can copy paste the code there is a
small call of my function at the end):
sr.map <- function(sr){
# This function converts the s(x,y) matrix into a function x 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)
if ( (x<0) && (y>0) ) # x<0,y>0
c(indx,ncol(sr)-indy+1)
else if ( (x>0) && (y>0) ) # x>0,y>0
c(nrow(sr)-indx+1,indy)
else if ( (x<0) && (y<0) ) # x>0,y<0
c(nrow(sr)-indx+1,indy)
else if ( (x>0) && (y<0) ) # x>0,y<0
c(indx,ncol(sr)-indy+1)
else
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)
If you are worried about my so many if inside the main body of my function you
can find why in the picture above. In the right part of the images you can see
some of my calculations
Top right part: What I wanted to have and what was the output was when there
was no if statement but only the last line c(indx,indy) (what two findIntervals
returned)
Based on the what I wanted (column on the top right part) I wrote the changes
in the logic by introducing if statements. You can find them at the bottom
right part.
This works fine for values close to the 'borders'
f.sr.map(-1,-1)
f.sr.map(-1,1)
f.sr.map(1,-1)
f.sr.map(1,1)
but not for values for example close to zero. This is a wrong output
f.sr.map(0.1,1)
[1] 3 6
I am sure that it might be an easier way to do all that so please inform me .
I would like to thank all of you for your kind efforts to help me
Best Regards
Alex
______________________________________________
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.
