plotting image/contour on irregular grid
On May 6, 2005, at 2:45 PM, Roger Bivand wrote:
On Fri, 6 May 2005, m p wrote:
Hello, I'd like to make a z(x,y) plot for irregularly spaced x,y. What are routines are available in R for this purpose?
One possibility is to interpolate a regular grid using interp() in the akima package, then use image() or contour(). Another is to use levelplot() with formula z ~ x + y in the lattice package, and the equivalent contourplot(); here, the x,y pairs must lie on a grid, but do not need to fill the grid (so are regularly spaced with missing grid cells).
You could also try tripack and rgl.triangles to produce piecewise linear surfaces on the Delaunay triangulation of the x,y points. Roger