[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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