[R] 2-dim density plot

[Duncan Murdoch]

On 11/08/2011 3:11 PM, annie Zhang wrote:
> Hi All,
>
> I have a 2-dim density defined on 0<x<1, 0<y<1, x<y. I know the exact
> formula of the density. How can I visualize it? What plot functions can I
> use?


persp() or contour() are in the graphics package.  There are similar 
ones in lattice (and I think in ggplot2), but I forget their names.  
There's also persp3d() in the rgl package for a rotatable version of 
persp().

Supposing f(x,y) gives the density at (x,y) (or NA if x > y), you plot 
it as follows:

x <- seq(0, 1, len=30)
y <- seq(0, 1, len=30)
z <- outer(x, y, f)
persp(x,y,z)
contour(x,y,z)
persp3d(x,y,z)

This relies on f() being vectorized; if it's not, use

z <- outer(x,y, Vectorize(f))

instead.

Duncan Murdoch