[R] density plot - beginner's question

[Deepayan Sarkar]

On Monday 13 January 2003 05:22 pm, Saurav Pathak wrote:
> Hi,
>
> I am trying to plot densities given on a two dimensional grid.  My
> data is in the an external file, and is arranged in three columns:
> x, y, density
>
> how may i get a plot of this?  i would like to get (1) a three
> dimensional plot and (2) a color coded two dimensional plot.

persp() for (1) and image() or filled.contour() for (2). Both need the density 
in the form of a matrix, as described in their respective help pages. 

Alternately, you could you the 3D functions in the lattice package:

library(lattice)
levelplot(density ~ x * y)

for (2).

wireframe(density ~ x * y)

will give you something similar to persp(), but it will be much slower.

>
> I have tried using
>
> 	image(x, y, density)
>
> but i am asked to put the data in ascending order.  i am not sure
> how i may put grid points in an ascending order.
>
> I would also like to know if i could use any other function, other
> than image.
>
> thank you in advance.