R/nnangle.R

In Zongzheng/forestSAS: An R package for forest spatial structure analysis systems

nnangle <-
function(nndist,nnx,nny){
  library(spatstat)
  xl<-as.data.frame(t(apply(nnx,1,function(x)cbind(x[2:5]-x[1]))))
  yl<-as.data.frame(t(apply(nny,1,function(x)cbind(x[2:5]-x[1]))))
  data1<-as.matrix(acos(yl/nndist)*sign(xl)*180/pi+360)
  data1[which(data1>360)]<-data1[which(data1>360)]-360
  data2<-data.frame(id=rownames(nndist),N=rownames(nndist),data1)
  data3<-split(data2[,-c(which(colnames(data2)==c("id","N")))],list(data2$N))
  data4<-as.data.frame(t(sapply((lapply(data3,sort)),as.matrix)))
  data5<-data4[rownames(nndist),]
  names(data5)<-c("A1","A2","A3","A4")
  angle1<-data5$A2-data5$A1
  angle2<-data5$A3-data5$A2
  angle3<-data5$A4-data5$A3
  angle4<-data5$A4-data5$A1
  nnangle<-cbind(angle1,angle2,angle3,angle4)
  nnangle[which(nnangle>180)]<-360-nnangle[which(nnangle>180)]
  nnangle<-data.frame(nnangle)
  rownames(nnangle)<-rownames(nndist)
  list(angle=data5,nnangle=nnangle)
}