[R-sig-Geo] Boundaries for kernel density estimation

[Rolf Turner]

On 30/09/11 06:30, Jennifer Crees wrote:
> Hi,
>
>
>
> I am carrying out kernel estimation on some species point data. However,
> the data are on a continental scale (many of the points hug the southern
> coastline of Europe) so that the analysis is including marine areas when
> the window is constructed around the point themselves. Is it possible to
> specify a boundary so that only the sampled terrestrial area will be
> included? Or perhaps it would be easier to look at local intensity?

If your boundary were all coastal, you could get what you want by
setting edge=FALSE in your call to density() --- I *think*!!!

However if some parts of your window boundary are coastline and
some parts are not, it looks tricky to me.  One idea might be to do
one intensity estimate with edge=FALSE, another with edge=TRUE,
and then somehow do a weighted average of the two with weights
determined by distance from coastline.  Points near the coastline
would get a high weight assigned to the edge=FALSE estimate and
a low weight to the edge=TRUE estimate.  And vice-versa.

Won't be too easy to implement, and it might be a load of dingos'
kidneys anyway --- it's just an idea off the top of my head.

I've cc-ed this message to Adrian Baddeley who may have a more
sound suggestion.  Here's hoping.

     cheers,

         Rolf Turner