pcds (version 0.1.6)

rv.tetraCC: The index of the \(CC\)-vertex region in a tetrahedron that contains a point

Description

Returns the index of the vertex whose region contains point p in a tetrahedron \(th=T(A,B,C,D)\) and vertex regions are based on the circumcenter \(CC\) of th. (see the plots in the example for illustrations).

The vertices of the tetrahedron th are labeled as \(1=A\), \(2=B\), \(3=C\), and \(4=C\) also according to the row number the vertex is recorded in th.

If the point, p, is not inside th, then the function yields NA as output. The corresponding vertex region is the polygon whose interior points are closest to that vertex. If th is regular tetrahedron, then \(CC\) and \(CM\) (center of mass) coincide.

See also (ceyhan:Phd-thesis,ceyhan:comp-geo-2010;textualpcds).

Usage

rv.tetraCC(p, th)

Value

A list with two elements

rv

Index of the \(CC\)-vertex region that contains point, p in the tetrahedron th

tri

The vertices of the tetrahedron, where row number corresponds to the vertex index in rv.

Arguments

p

A 3D point for which \(CC\)-vertex region it resides in is to be determined in the tetrahedron th.

th

A \(4 \times 3\) matrix with each row representing a vertex of the tetrahedron.

Author

Elvan Ceyhan

References

See Also

rv.tetraCM and rv.triCC

Examples

if (FALSE) {
set.seed(123)
A<-c(0,0,0)+runif(3,-.2,.2);
B<-c(1,0,0)+runif(3,-.2,.2);
C<-c(1/2,sqrt(3)/2,0)+runif(3,-.2,.2);
D<-c(1/2,sqrt(3)/6,sqrt(6)/3)+runif(3,-.2,.2);
tetra<-rbind(A,B,C,D)

n<-20  #try also n<-40

Xp<-runif.tetra(n,tetra)$g

rv.tetraCC(Xp[1,],tetra)

Rv<-vector()
for (i in 1:n)
 Rv<-c(Rv,rv.tetraCC(Xp[i,],tetra)$rv)
Rv

CC<-circ.cent.tetra(tetra)
CC

Xlim<-range(tetra[,1],Xp[,1],CC[1])
Ylim<-range(tetra[,2],Xp[,2],CC[2])
Zlim<-range(tetra[,3],Xp[,3],CC[3])
xd<-Xlim[2]-Xlim[1]
yd<-Ylim[2]-Ylim[1]
zd<-Zlim[2]-Zlim[1]

plot3D::scatter3D(tetra[,1],tetra[,2],tetra[,3], phi =0,theta=40, bty = "g",
main="Scatterplot of data points \n and CC-vertex regions",
xlim=Xlim+xd*c(-.05,.05),ylim=Ylim+yd*c(-.05,.05), zlim=Zlim+zd*c(-.05,.05),
          pch = 20, cex = 1, ticktype = "detailed")
L<-rbind(A,A,A,B,B,C); R<-rbind(B,C,D,C,D,D)
plot3D::segments3D(L[,1], L[,2], L[,3], R[,1], R[,2],R[,3], add=TRUE,lwd=2)
#add the data points
plot3D::points3D(Xp[,1],Xp[,2],Xp[,3],pch=".",cex=3, add=TRUE)

plot3D::text3D(tetra[,1],tetra[,2],tetra[,3], labels=c("A","B","C","D"), add=TRUE)
plot3D::text3D(CC[1],CC[2],CC[3], labels=c("CC"), add=TRUE)

D1<-(A+B)/2; D2<-(A+C)/2; D3<-(A+D)/2; D4<-(B+C)/2; D5<-(B+D)/2; D6<-(C+D)/2;
L<-rbind(D1,D2,D3,D4,D5,D6); R<-matrix(rep(CC,6),ncol=3,byrow=TRUE)
plot3D::segments3D(L[,1], L[,2], L[,3], R[,1], R[,2],R[,3], add=TRUE,lty=2)

F1<-int.line.plane(A,CC,B,C,D)
L<-matrix(rep(F1,4),ncol=3,byrow=TRUE); R<-rbind(D4,D5,D6,CC)
plot3D::segments3D(L[,1], L[,2], L[,3], R[,1], R[,2],R[,3],col=2, add=TRUE,lty=2)

F2<-int.line.plane(B,CC,A,C,D)
L<-matrix(rep(F2,4),ncol=3,byrow=TRUE); R<-rbind(D2,D3,D6,CC)
plot3D::segments3D(L[,1], L[,2], L[,3], R[,1], R[,2],R[,3],col=3, add=TRUE,lty=2)

F3<-int.line.plane(C,CC,A,B,D)
L<-matrix(rep(F3,4),ncol=3,byrow=TRUE); R<-rbind(D3,D5,D6,CC)
plot3D::segments3D(L[,1], L[,2], L[,3], R[,1], R[,2],R[,3],col=4, add=TRUE,lty=2)

F4<-int.line.plane(D,CC,A,B,C)
L<-matrix(rep(F4,4),ncol=3,byrow=TRUE); R<-rbind(D1,D2,D4,CC)
plot3D::segments3D(L[,1], L[,2], L[,3], R[,1], R[,2],R[,3],col=5, add=TRUE,lty=2)

plot3D::text3D(Xp[,1],Xp[,2],Xp[,3], labels=factor(Rv), add=TRUE)
}