nlme: spatial autocorrelation on a sphere
On Oct 1, 2012, at 12:59 AM, Dan Bebber wrote:
Thanks, but the problem is quite specific and not addressed on the Spatial Data taskview page. Quite specifically, I would like to know how to edit corSpatial functions to calculate great circle distances. The Bayesian equivalent, georamps in the ramps package, is able to do this, therefore I imagine it must be possible for nlme.
Can't you use the corStruct functions in pkg::ramps? They allow specification of the 'haversine' metric. The corR* functions inherit from class corStruct.
David. > Dan > ________________________________________ > From: David Winsemius [dwinsemius at comcast.net] > Sent: 01 October 2012 08:38 > To: Dan Bebber > Cc: r-help at r-project.org > Subject: Re: [R] nlme: spatial autocorrelation on a sphere > > On Sep 30, 2012, at 6:48 PM, Dan Bebber wrote: > >> I have spatial data on a sphere (the Earth) for which I would like to run an gls model assuming that the errors are autcorrelated, i.e. including a corSpatial correlation in the model specification. >> >> In this case the distance metric should be calculated on the sphere, therefore metric = "euclidean" in (for example) corSpher would be incorrect. >> >> I would be grateful for help on how to write a new distance metric for the corSpatial function. >> I believe there are several ways that distances on a sphere can be calculated in R, for example the "distMeeus" function in the geosphere library. However, I have no idea how to write this into a corSpatial function. >> >> The aim is to end up with a metric = "sphere" option that calculates great circle distances between points using latitude and longitude. > > LMCTVTFY: http://cran.r-project.org/web/views/Spatial.html > > -- > > David Winsemius, MD > Alameda, CA, USA > > David Winsemius, MD Alameda, CA, USA