Thank you so much, Michael and Duncan. It worked.

Annie

On Thu, Aug 11, 2011 at 2:23 PM, Duncan Murdoch <murdoch.duncan@gmail.com>wrote:

>  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
>

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