[R] Get contour of a map

[Barry Rowlingson]

On Mon, May 23, 2011 at 8:00 PM, Duncan Murdoch
<murdoch.duncan at gmail.com> wrote:
> On 11-05-23 5:55 AM, Pierre Bruyer wrote:

>
> I think writing that would be hard, but you can fake it.  Find the range of
> z first to work out the contour levels you want, then put very large values
> around the outside of the z matrix.  (You can't use Inf, but big finite
> values will work.)

 I had a play with this yesterday, expecting gPolygonize from rgeos to
do the heavy lifting. But all I could make it do with contours from
the standard volcano data, converted to the appropriate SpatialLines
form, was segfault. Works fine on the examples given in the
gPolygonize docs.

 That was an end-of-day ten minute experiment, so I might have another go later.

B