Xin.convex.hullY {pcds}

Points from one class inside the convex hull of the points from the other class

Description

Given two 2D data sets, Xp and Yp, it returns the Xp points inside the convex hull of Yp points.

See (Okabe et al. (2000); Ceyhan (2010); Sinclair (2016)) for more on Delaunay triangulation and the corresponding algorithm.

Usage

Xin.convex.hullY(Xp, Yp)

Arguments

Xp

A set of 2D points which constitute the data set.

Yp

A set of 2D points which constitute the vertices of the Delaunay triangles.

Value

Xp points inside the convex hull of Yp points

Author(s)

Elvan Ceyhan

References

Ceyhan E (2010). “Extension of One-Dimensional Proximity Regions to Higher Dimensions.” Computational Geometry: Theory and Applications, 43(9), 721-748.

Okabe A, Boots B, Sugihara K, Chiu SN (2000). Spatial Tessellations: Concepts and Applications of Voronoi Diagrams. Wiley, New York.

Sinclair D (2016). “S-hull: a fast radial sweep-hull routine for Delaunay triangulation.” 1604.01428.

See Also

plotDelaunay.tri

Examples

#nx is number of X points (target) and ny is number of Y points (nontarget)
nx<-20; ny<-5;  #try also nx<-40; ny<-10 or nx<-1000; ny<-10;

set.seed(1)
Xp<-cbind(runif(nx,0,1),runif(nx,0,1))
Yp<-cbind(runif(ny,0,.25),runif(ny,0,.25))+cbind(c(0,0,0.5,1,1),c(0,1,.5,0,1))
#try also Yp<-cbind(runif(ny,0,1),runif(ny,0,1))

DT<-interp::tri.mesh(Yp[,1],Yp[,2],duplicate="remove")

Xlim<-range(Xp[,1],Yp[,1])
Ylim<-range(Xp[,2],Yp[,2])
xd<-Xlim[2]-Xlim[1]
yd<-Ylim[2]-Ylim[1]

Xch<-Xin.convex.hullY(Xp,Yp)

plot(Xp,main=" ", xlab=" ", ylab=" ",
xlim=Xlim+xd*c(-.05,.05),ylim=Ylim+yd*c(-.05,.05),pch=".",cex=3)
interp::convex.hull(DT,plot.it = TRUE, add = TRUE)  # or try polygon(Yp[ch$i,])
points(Xch,pch=4,col="red")