[R-sig-Geo] spatial sampling with an un-ordered polygon for which links between points are known

[Paolo Piras]

Hi folks,
I write in order to know if there is a solution to the following spatial sampling problem:
I have a polygon that is not ordered; however, I know the "links" (or edges) between points;
I need to sample 2000 points within the polygon. Using spsample() and Polygon() I need an ordered polygon which is not the case.
I tried to use the links information in order to dynamically (and generalizing the problem) obtain the correct
order but I did'nt get effective solution. I dont want an "estimate" of the hull from points or other heuristic strategies; I want to use the links info in order to properly sort my points.
Here below a fully reproducible example.

library(sp)
pol<-matrix(c(30.24854,33.90530,27.48992,30.21646,40.03200,39.26215,33.52038,39.10177,39.99992,47.02477,47.44176,55.17230,57.38561,55.30061,57.25730,57.38561,28.45223,21.78023,31.21084,33.96946,22.10100,22.96708,40.86600,40.06407,40.83392,38.13946,24.79546,29.70323,30.60138,33.61661,31.65992,32.68638),ncol=2)
plot(pol,asp=1)
text(pol[,1],pol[,2],c(1:nrow(pol))) ### as you can see the polygon is not ordered
links<-matrix(c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,2,6,1,3,11,5,4,7,8,9,12,13,15,10,16,14),ncol=2)
for(i in 1:nrow(links)){
  segments(pol[links[i,1],1],pol[links[i,1],2],pol[links[i,2],1],pol[links[i,2],2])
} # Fortunately I will have always these links
#### now I would like to sampling,regularly, say 2000 points in the polygon
sfe1<-spsample(Polygon(pol),2000,type="regular")
points(sfe1 at coords) ###  of course this is not what I want.
####  using an "ad hoc" ordering
correct<-c(1,2,6,5,11,12,13,15,16,14,10,9,8,7,4,3) ## this is just an "ad hoc" solution; I need to generalize using the links information
sfe1<-spsample(Polygon(pol[correct,]),2000,type="regular")
points(sfe1 at coords,col=2,pch=19,cex=0.3) ### this is what I want.

This is an ad hoc solution; as I will have many different polygons (thounsed) and all different (some very irregular) but always with links information I would like to know if there is a solution to get the correct order using links.
Thanks in advance for any advice
All the best
Paolo


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