Dear list, following the vignette of the package 'spacemmakeR' I have built a gabriel graph of ten randomly placed points: library(spdep) set.seed(3) xyir<-matrix(runif(20),10,2) nbgab<-graph2nb(gabrielneigh(xyir), sym=TRUE) plot(nbgab,xyir,points=FALSE) points(xyir,pch=20,cex=2,col=c(2,4,4,4,2,2,4,2,4,4)) title(main="Gabriel Graph") Now, I need to determine for any additional point whether it is located within the region surrounded by links between identically colored points. Would anybody give me a hint how to a achieve this? Thanks in advance, Ond?ej Mikula -- Ond?ej Mikula Institute of Animal Physiology and Genetics Academy of Sciences of the Czech Republic Veveri 97, 60200 Brno, Czech Republic Institute of Vertebrate Biology Academy of Sciences of the Czech Republic Studenec 122, 67502 Konesin, Czech Republic