[R] nlme: spatial autocorrelation on a sphere
dwinsemius at comcast.net
Mon Oct 1 11:15:01 CEST 2012
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.
> 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
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