On Thu, Apr 23, 2009 at 4:22 AM, Jaakko Nevalainen
<jaakko.nevalai...@uta.fi> wrote:
> Dear R-users:
>
> The following code produces two cones in two panels. What I would like to
> have is to have them in one, and to meet in the origin. Does anyone have any
> good ideas how to do this?
wireframe gets easily confused when not all (x, y) combinations in the
grid are present in your data. It's safer to set the z-values to NA if
you want to omit them. This should be a good start:
gstar <- g
gstar$z[!ind0] <- NA
gstar$z2 <- -gstar$z
wireframe(z + z2 ~ x * y, gstar, colorkey=TRUE,drape=TRUE,
scales=list(arrows=FALSE))
If you really want to combine surfaces defined on different (x,y)
grids, probably the only safe way is to combine them into a single
grid.
-Deepayan
>
> Thanks for your help
>
> Jaakko
>
> library(lattice)
>
> A<-matrix(ncol=2, nrow=64)
>
> for(i in 0:63)
> {
> A[i+1,1]<-sin(i/10)
> A[i+1,2]<-cos(i/10)
> }
>
> Sigma<-matrix(c(0.5,0.1,0.1,0.25),byrow=TRUE,nrow=2)
> G<-eigen(Sigma)
>
> E1<-t(G$vector%*%t(A))
> E2<-t(diag(sqrt(G$values))%*%t(E1))
> mu<-c(0.1,0.2)
> E3<-sweep(E2,2,-mu)
>
> a<-sqrt(max(rowSums(sweep(E3,2,mu)**2)))
> b<-sqrt(min(rowSums(sweep(E3,2,mu)**2)))
>
> astar<-as.numeric(a+abs(mu[1]))
> bstar<-as.numeric(b+abs(mu[2]))
>
> xstar<-seq(-astar,astar,len=50)
> ystar<-seq(-bstar,bstar,len=50)
>
> g<-expand.grid(x=xstar,y=ystar)
>
> p1<-2*g$x*mu[1]/a**2+2*g$y*mu[2]/b**2
> p2<-(g$x**2/a**2+g$y**2/b**2)
> p3<-mu[1]**2/a**2+mu[2]**2/b**2-1
>
> q<-(p1+sqrt(p1**2-4*p2*p3))/(2*p2)
> z<-sqrt(1-(q*g$x)**2-(q*g$y)**2)
> zstar<-(z/q)
> ind0<-!(q<1)
> g$z<-zstar
> sc<-matrix(c(rep(c(-1,-1,-1),sum(ind0))),nrow=sum(ind0),byrow=TRUE)
> gstar<-rbind(g[ind0,],sc*g[ind0,])
>
> group<-c(rep(1,nrow(gstar)/2),rep(2,nrow(gstar)/2))
> gstar$group<-group
>
> wireframe(z~x*y|group,gstar,colorkey=TRUE,drape=TRUE,
> scales=list(arrows=FALSE))
>
> ______________________________________________
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>
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