With package gdistance, currently under development on R-Forge, it is possible to calculate a number of "non-Euclidean" distances, including the least-cost distance (based on package igraph), resistance distance, and (soon) randomised shortest paths.
Jacob van Etten --- On Wed, 1/27/10, Pilar Tugores Ferra <pilar.tugo...@ba.ieo.es> wrote: From: Pilar Tugores Ferra <pilar.tugo...@ba.ieo.es> Subject: Re: [R-sig-Geo] kriging as fish swim, not as crows fly To: "Martin Renner" <martin.ren...@stonebow.otago.ac.nz> Cc: r-sig-geo@stat.math.ethz.ch Date: Wednesday, January 27, 2010, 5:35 PM Hi, Martin Two years ago there was a similar discussion on the list: http://markmail.org/message/tw7ulpxbgixieyys If I understand it properly, your problem is you need to compute your variogram using non-euclidian distances. As far as I know, there is no package in R that can do so (correct me if I am wrong). There is a function LCP_Krige that I think you can find on the net. It is not an R function but a mixture of ArcGis 8.x and Matlab. Maybe you can use it or try to adapt it to R... Jensen, OP, MC Christman and TJ Mller. 2006. Landscape-based geostatistics: a case study of the distribution of blue crab in Chesapeake Bay. Envirometrics. 17:605-621. I was interested in applying this sort of analysis but I didn't suceed. I hope you are more lacky! Cheers, Pilar Mª Pilar Tugores Ferrà PhD Student Instituto Español de Oceanografía Centro Oceanográfico de Baleares Muelle de Poniente s/n 07015 Palma de Mallorca Baleares, España Telf.: (34) 971 133759 -----Mensaje original----- De: r-sig-geo-boun...@stat.math.ethz.ch [mailto:r-sig-geo-boun...@stat.math.ethz.ch] En nombre de Michael Sumner Enviado el: 27 January 2010 10:29 Para: Martin Renner CC: r-sig-geo@stat.math.ethz.ch Asunto: Re: [R-sig-Geo] kriging as fish swim, not as crows fly Not kriging as such, but check out the soap-film smoothing in package mgcv: http://www.maths.bath.ac.uk/~sw283/simon/papers/soap.pdf FWIW, there are binning methods with MCMC in the package tripEstimation that have similar features, but they are particularly focussed on individual track estimation and probably not easily applied. Is location uncertainty a big issue for your data? What are the input locations? Cheers, Mike. On Wed, Jan 27, 2010 at 7:06 PM, Martin Renner <martin.ren...@stonebow.otago.ac.nz> wrote: > Hi All, > > I want to kirg fish and seabird densities within an estuary which has several > arms. Since neither organisms cross land, the appropriate distances would not > be euclidian but over-water (as fish swim). There are several papers, > describing this problem and how to deal with it (see below), but I have not > found an easily accessible implementation. Is anybody aware of a solution in > R? > > Best, > Martin > > > > @article{Rathbun:1998aa, > Author = {Rathbun, Stephen L.}, > Journal = {Environmetrics}, > Number = {2}, > Pages = {109--129}, > Title = {Spatial modelling in irregularly shaped regions: kriging > estuaries}, > Volume = {9}, > Year = {1998}} > > @article{Little:1997aa, > Author = {Little, Laurie S. and Edwards, Don and Porter, Dwayne E.}, > Journal = {Journal of Experimental Marine Biology and Ecology}, > Number = {1}, > Pages = {1--11}, > Title = {Kriging in estuaries: as the crow flies, or as the fish > swims?}, > Volume = {213}, > Year = {1997}} > > > > > Martin Renner > US Geological Survey > Alaska Science Center > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo [[alternative HTML version deleted]]
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