[R] Creating smooth color regions with panel.contourplot()

[Waichler, Scott R]

When I use panel.contourplot() with filled color regions, the coloring
follows the stair-step edge of the underlying grid instead the smooth
contour lines themselves.  How can I get the latter behavior?  I would
guess there is a much simpler way than manually creating polygons with
contourLines(), especially since a contour interval/region can have
holes inside it (different contour intervals).

Thanks,
Scott Waichler
Pacific Northwest National Laboratory
scott.waichler at pnl.gov