Re: [R] Plot a sphere

[Spencer Graves]

     A hemisphere is relatively easy;  try the following: 

     x <- seq(-1, 1, length=21)
     Z <- outer(x, x, function(x, y)sqrt(1-x^2-y^2))
     persp(x=x, y=x, z=Z)
     A contour plot is also relatively easy: 

     image(x=x, y=x, z=Z)
     contour(x=x, y=x, z=Z, add=T)
     However, if you want an honest perspective plot of a sphere 
complete with the underside, etc., I know of nothing in R that could do 
that.  S-Plus has "perspp", which could be used.  However, that seems to 
be one of the few features available in S-Plus that is not currently 
available in R. 

      hope this helps. 
     spencer graves

Derick Schoonbee wrote:

Hi,

I'm new to R (and math ;) Would somebody please be so kind as to 
direct me in plotting a 3D sphere?

I tried something in the lines of:
####
y <- x <- seq(-pi, pi, length=pi*10)
f <- function(x,y)
{
    z <- sqrt(pi - x^2 - y^2)
    #z[is.na(z)] <- 0
    z
}
z <- outer(x, y, f)
persp(x, y, z, theta = 120, phi = 30)
####
I've also tried: .... make.surface.grid(...) .. persp( as.surface( 
grid, z) ) ... with the same result: 'Incomplete' demi sphere and 
others..

Any suggestions/solutions would be appreaciated.

Regards,
Derick
PS:Merry X-mas ;)

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