[R-sig-Geo] [FORGED] Re: [FORGED] kernel density: units of bandwidth
tyatabe at ucdavis.edu
Mon Feb 22 22:58:23 CET 2016
Sorry, Rolf. I didn't realize I was replying only to you!
Thanks for your reply. I'll project before making the ppp object that I'll
use in my Kernel.
On Mon, Feb 22, 2016 at 1:53 PM, Rolf Turner <r.turner at auckland.ac.nz>
> On 23/02/16 10:34, Tadaishi Yatabe-Rodriguez wrote:
> Thanks, Rolf. This ,makes it clearer. I've another question though: the
>> ppp object I get the Kernel density from is not projected, then what
>> would be the unit of projection of this un-projected object? The
>> projection of the object from which it was created from (e.g.
>> SpatialPoints object)?
>> Thanks again,
> You should probably keep this discussion on-list; others who subscribe to
> the list are much more knowledgeable than I and may have useful
> contributions to make (and may correct my errors). I have taken the
> liberty of including the list in my reply.
> I think that your question is not well-posed. The density.ppm() function
> treats the coordinates of points as Euclidean coordinates (with the same
> units on both the x and y axes). If your point pattern is "un-protected"
> then I presume that x and y are in longitude and latitude in which case the
> coordinates are not Euclidean and the x and y axis units are different,
> since longitude and latitude are constructed in different ways.
> If the region in question is "small" (and not too near either pole, I
> guess) then this probably doesn't make much difference, and the units of
> sigma would, roughly speaking, be "degrees". Otherwise it seems to me
> there is no meaningful answer to your question.
> It would probably be best to project your data before forming the ppp
> Ege has been doing some work on point patterns on the sphere which might
> possibly be of relevance here. He may feel like chiming in on this issue.
> Technical Editor ANZJS
> Department of Statistics
> University of Auckland
> Phone: +64-9-373-7599 ext. 88276
DVM, MPVM, PhD (C)
Center for Animal Disease Modeling and Surveillance (CADMS)
Department of Medicine and Epidemiology
School of Veterinary Medicine
University of California Davis
[[alternative HTML version deleted]]
More information about the R-sig-Geo