[R] plot contour map for irregular data points

[Andre Jung]

Yes, contourplot() takes irregular spaced values, but you need a regular 
grid to project the data on to.

grid <- expand.grid(x=x,y=y);
contourplot(z~x*y,grid,cuts=50);

This gives me a plot with little coloured areas around my datapoints only.

A better way for me was to

library(akima);
data.interp <- interp(x,y,z);
image(data.interp); #or
contour(data.interp);

where interp() leaves you with multiple options of interpolation 
(linear, spline, ...).

For further reading I recommend:
https://stat.ethz.ch/pipermail/r-help/2005-October/080853.html
https://stat.ethz.ch/pipermail/r-help/2003-December/043897.html
https://stat.ethz.ch/pipermail/r-sig-geo/2005-October/000609.html

cheers,
andre


S Ellison wrote:
 > Doesn't the lattice package's contourplot take arbitrary x and y?
 >
 > library(lattice)
 > ?contourplot