[R] get vector data from contour

Ross Ihaka ihaka at stat.auckland.ac.nz
Mon Feb 5 20:45:20 CET 2001

On 2001.02.06 00:26:45 +1300 Thomas Petzoldt wrote:

> I have carried out a spatial interpolation (Kriging) using surf.gls() 
> The contour plot looks very plausible and the image plot is o.k too. 
> The problem is, hovever, that I need the vectorized isoplethes, as in
> contour().
> Unfortunately, I found no solution to get the internal data from
> contour().
> Is there a possibility to extract contour lines as x-y-polygon from a
> grid without hacking plot3d.c?

I can't offer another solution, but I would be very interested in anything
you come up with. I would like to see all R graphics code separated into
computation and drawing components. This would make a number of things
easier - eg. replacing the current drawing system with something better.

I the case of contour, I can see a couple of issues. (1) joining contour
lines which intersect the boundary by following the boundary (2) dealing
with missing values.


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