[R] Get contour of a map

[Pierre Bruyer]

My main problem is to use a spline cubic smooth (I hope this understanding, my english is not perfect ... ), and I would like to smooth the contours of my maps with my own scale of levels (e.G., levels are 1,3,5,10,20,30,40,50,75,...) so it is not easy to find a function which consider this two constrains, and I don't see how gPolygon can help me (in it doc, I have seen this function cut polygon in a set of subpolygon.


Le 24 mai 2011 à 10:18, Barry Rowlingson a écrit :

> 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