I try to find a circular filter that I can export to be used in a
spatial software.
Assuming, we have a matrix, representing 9x9 regularly spaced points
with the center point 'filter[5, 5]'. In this example, I want to find a
function that weighs all neighbor points within a distance of d=4 units
with 1:
> filter <- matrix(0, 9, 9)
> filter <- function() ...
> filter
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
[1,] 0 0 0 0 1 0 0 0 0
[2,] 0 0 1 1 1 1 1 0 0
[3,] 0 1 1 1 1 1 1 1 0
[4,] 0 1 1 1 1 1 1 1 0
[5,] 1 1 1 1 1 1 1 1 1
[6,] 0 1 1 1 1 1 1 1 0
[7,] 0 1 1 1 1 1 1 1 0
[8,] 0 0 1 1 1 1 1 0 0
[9,] 0 0 0 0 1 0 0 0 0
Finally, I want to use a larger matrix, e.g. with 61x61 points. Is
there a simple function around that I could use to this end?
Thanks!
Christof
try:
filter.matrix.center<-function(n=9,size=5){
x<-matrix(1,n,n)
center<-(n+1)/2
(abs(row(x)-center)+abs(col(x)-center)) < size
}
filter.matrix.center()
some tests:
> 0+filter.matrix.center(5,2)
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 0
[2,] 0 0 1 0 0
[3,] 0 1 1 1 0
[4,] 0 0 1 0 0
[5,] 0 0 0 0 0
> 0+filter.matrix.center()
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
[1,] 0 0 0 0 1 0 0 0 0
[2,] 0 0 0 1 1 1 0 0 0
[3,] 0 0 1 1 1 1 1 0 0
[4,] 0 1 1 1 1 1 1 1 0
[5,] 1 1 1 1 1 1 1 1 1
[6,] 0 1 1 1 1 1 1 1 0
[7,] 0 0 1 1 1 1 1 0 0
[8,] 0 0 0 1 1 1 0 0 0
[9,] 0 0 0 0 1 0 0 0 0
Peter Wolf
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Christof Bigler wrote:
I try to find a circular filter that I can export to be used in a
spatial software.
Assuming, we have a matrix, representing 9x9 regularly spaced points
with the center point 'filter[5, 5]'. In this example, I want to find a
function that weighs all neighbor points within a distance of d=4 units
with 1:
> filter <- matrix(0, 9, 9)
> filter <- function() ...
> filter
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
[1,] 0 0 0 0 1 0 0 0 0
[2,] 0 0 1 1 1 1 1 0 0
[3,] 0 1 1 1 1 1 1 1 0
[4,] 0 1 1 1 1 1 1 1 0
[5,] 1 1 1 1 1 1 1 1 1
[6,] 0 1 1 1 1 1 1 1 0
[7,] 0 1 1 1 1 1 1 1 0
[8,] 0 0 1 1 1 1 1 0 0
[9,] 0 0 0 0 1 0 0 0 0
Finally, I want to use a larger matrix, e.g. with 61x61 points. Is there
a simple function around that I could use to this end?
Thanks!
Christof
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Christof Bigler wrote:> I try to find a circular filter that I can export to be used in a > spatial software. > Assuming, we have a matrix, representing 9x9 regularly spaced points > with the center point 'filter[5, 5]'. In this example, I want to find a > function that weighs all neighbor points within a distance of d=4 units > with 1: > > > filter <- matrix(0, 9, 9) > > filter <- function() ... > > filter > [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] > [1,] 0 0 0 0 1 0 0 0 0 > [2,] 0 0 1 1 1 1 1 0 0 > [3,] 0 1 1 1 1 1 1 1 0 > [4,] 0 1 1 1 1 1 1 1 0 > [5,] 1 1 1 1 1 1 1 1 1 > [6,] 0 1 1 1 1 1 1 1 0 > [7,] 0 1 1 1 1 1 1 1 0 > [8,] 0 0 1 1 1 1 1 0 0 > [9,] 0 0 0 0 1 0 0 0 0 > > Finally, I want to use a larger matrix, e.g. with 61x61 points. Is there > a simple function around that I could use to this end?I don't know whether there is a function makeYourFilter(), but I'm pretty sure it's easy to write it. Unfortunately, I don't know which distance you are talking about. Uwe Ligges> Thanks! > Christof > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html