test of spatial dependence?? - ask an ecologist?
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 <milton_ruser at yahoo.com.br> 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 <dfarrar at newrvana.com> 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]]
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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: Roger.Bivand at nhh.no