[R] Get contour of a map

[David Winsemius]

On May 23, 2011, at 5:55 AM, Pierre Bruyer wrote:

> Hello everybody,
>
> I search a function which returns the contour of map with levels  
> like contourLines, but I would like this function return the border  
> of the map too, because the function contourLines cannot consider  
> the corner of the map and it is not adapted to fill polygon after  
> that.

Frank Harrell has a `perimeter` function in his `rms` package which he  
uses to establish (and optionally draw)  boundaries around 2D regions  
with sufficient data to yield meaningful estimates. The plotting is  
handed off to lattice functions. His default plotting function for 2D  
plotting is contourplot. It didn't take that long to make the  
transition to rms+lattice and I have been very pleased with the  
integration of the two.

There is also a chull  (convex hull) function although at the moment I  
do not remember which package it resides in.


>
> Thanks in advance
>
> Pierre Bruyer
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David Winsemius, MD
West Hartford, CT