[R-sig-Geo] quilt.plot

Hi, I'm am layering two quilt.plot functions on the same plot. The first is a number of points with a scale that has been grayed out just to show the location of the data. The second layer has colors, but only those data points with statistically significant data are shown, which means that

[R-sig-Geo] plotting x y z data from an irregular grid

Hi, I'm trying to plot some data (z) that is linked to latlong coordinates (xy). These coordinates are not however on a regular grid. I also have some shapefiles on which I would like to overlay the data. I can plot the shapefiles (country/city outlines) and overplot the data, but