pcds (version 0.1.4)

circ.cent.tri: Circumcenter of a general triangle

Description

Returns the circumcenter a given triangle, tri, with vertices stacked row-wise. See (weisstein-tri-centers,ceyhan:comp-geo-2010;textualpcds) for triangle centers.

Usage

circ.cent.tri(tri)

Value

circumcenter of the triangle tri

Arguments

tri

Three 2D points, stacked row-wise, each row representing a vertex of the triangle.

Author

Elvan Ceyhan

References

See Also

circ.cent.bastri

Examples

A<-c(1,1); B<-c(2,0); C<-c(1.5,2);
Tr<-rbind(A,B,C);  #the vertices of the triangle Tr

CC<-circ.cent.tri(Tr)  #the circumcenter
CC

D1<-(B+C)/2; D2<-(A+C)/2; D3<-(A+B)/2; #midpoints of the edges
Ds<-rbind(D1,D2,D3)

Xlim<-range(Tr[,1],CC[1])
Ylim<-range(Tr[,2],CC[2])
xd<-Xlim[2]-Xlim[1]
yd<-Ylim[2]-Ylim[1]

oldpar <- par(no.readonly = TRUE)
par(pty="s")
plot(A,asp=1,pch=".",xlab="",ylab="",axes=TRUE,xlim=Xlim+xd*c(-.05,.05),ylim=Ylim+yd*c(-.05,.05))
polygon(Tr)
points(rbind(CC))
L<-matrix(rep(CC,3),ncol=2,byrow=TRUE); R<-Ds
segments(L[,1], L[,2], R[,1], R[,2], lty=2)

txt<-rbind(Tr,CC,Ds)
xc<-txt[,1]+c(-.08,.08,.08,.12,-.09,-.1,-.09)
yc<-txt[,2]+c(.02,-.02,.03,-.06,.02,.06,-.04)
txt.str<-c("A","B","C","CC","D1","D2","D3")
text(xc,yc,txt.str)
par(oldpar)

A<-c(0,0); B<-c(1,0); C<-c(1/2,sqrt(3)/2);
Te<-rbind(A,B,C);  #the vertices of the equilateral triangle Te
circ.cent.tri(Te)  #the circumcenter

A<-c(0,0); B<-c(0,1); C<-c(2,0);
Tr<-rbind(A,B,C);  #the vertices of the triangle T
circ.cent.tri(Tr)  #the circumcenter

dat.fr<-data.frame(a=Tr)
circ.cent.tri(dat.fr)