Although you don't have coordinates, there has to be some kind of information on spatial relationships. (I am likely saying the same thing as Roger.) Let me see if I have this right. Some large area is partitioned into "cells" (polygons in an ArcInfo shape file?) and, within each cell you compute something. Then the distance between any two cells may be zero or one, one for any pair of cells that are adjacent, zero for any pair not adjacent. It doesn't strike me as that odd a situation and so I think I would like to know what is a conventional solution. One possibility would be to use Euclidean distances among centroids of cells. I have not reviewed the basis of the Mantel tests used by ecologists. If that is what you need, in looking for a program we would need to be mindful of the fact that a probably different "Mantel test" is used routinely for evaluation of disease data, in particular specialized as the "logrank test" of survival analysis. regards, Farrar
Roger Bivand <[EMAIL PROTECTED]> wrote: On Wed, 6 Dec 2006, Xu Yuan wrote: > Thanks David and Milton for replies. No, I don't have the coordiates. > In other words, my data are not point data. But I think there is a way > to test of spatial dependence for areal data or lattice data. In this > case, the variable of interest is typically the average value of an > area instead of a point. Do you how to do this? But do you know where the areas are in relation to each other? Does the spatialCovariance package help? Roger > > Thank you. > Xu > > On 12/6/06, Milton Cezar Ribeiro wrote: > > > > I never used it, but I beleave that it is a job for "mantel.rtest()" > > available on "ade4" package. > > > > In fact Farrar are right, you will neet the XY coordinates. Give a look at > > "Legendre & Legendre" text book. > > > > HTH, > > > > Miltinho > > Brazil > > > > David Farrar escreveu: > > > > > > In addition to the 25 numbers, I assume you have coordinates of each field. > > Otherwise, I don't understand what you are trying to do. I think ecologists > > like to use a test due to Mantel in this situation. > > > > The prefix "auto" means "self," of course, the idea being that measurements > > of the same variable under different conditions are correlated. I guess > > this would be a case of "autodependence." For correlation versus > > dependence, check your intro stats book. > > > > de nada, > > X'X > > > > Farrar > > > > > > Xu Yuan wrote: > > hello R-friends, > > > > I am a R beginner and try to ask a basic question: > > > > How to test the spatial dependence of a column of data? for example, I have > > 25 agricultural fields, and I measure the average slope (%) or pH for each > > field. All I have is 25 numbers. > > > > PS, could someone confirm that "spatial dependence" is equivalent to > > "spatial correlation" or "spatial autocorrelation" or not. > > > > Thank you very much. > > XY > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > [email protected] mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > [email protected] mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > > > > > > ________________________________ > O Yahoo! está de cara nova. Venha conferir! > > > > > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: [EMAIL PROTECTED] ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]]
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