On Wed, 15 Mar 2006, zhijie zhang wrote: > hi,friends, > we all know that moran's I index and Geary'C index can be used to test > spatial autocorrelation in both the area data and point data, but i only can > find something on how to calculate on the data of area, and can't find the > methods to perform it on the point data, could anybody give me some > information, thanks in advance!
There is no difference between area and point data given a Voronoi/Dirichlet tesselation. To use any such index, you are obliged to define neighours anyway, and whether you use a distance criterion, k-nearest neighbours, triangulation, or a graph criterion such as a minimum spanning tree, the duality remains. Functions for defining neighbours are found in ade4 and spdep, and suit points at least adequately. If you want a distance-based correlogram, define increasing distance bands (or see the off-CRAN ncf package). The functions are (among others) mstree() in ade4 taking a distance matrix as its argument, and dnearneigh(), knearneigh(), tri2nb(), gabrielneigh(), relativeneigh(), and soi.graph() taking a matrix of 2D coordinates as their argument in spdep (if your points are a regular grid, there is also cell2nb()). At least you have a choice here. > > -- > Kind Regards, > Zhi Jie,Zhang ,PHD > Department of Epidemiology, School of Public Health, Fudan University > Tel:86-21-54237149 > > [[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 > -- 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
