Help on computing Geary's C statistic to test for Spatial Autocorrelation
R User <ruser180 <at> gmail.com> writes:
Dear Users: I have been trying to use the geary.test() function in *R*, but am having slight difficulty understanding how I am to apply it in my context. I have 2 matrices: 1) *n x p* matrix of *n* observations with *p* measurements each. It may be noted that this matrix has a spatial dimension to it, as the *n*observations are at different geographical locations on a map. 2) *n x n* spatial weights matrix (symmetric) with each matrix element being an inter-locality weight.
You sent this message to me off-list, as well as to this list, not R-sig-geo. Using a general list for specific questions is not a good idea, and asking on the list after expecting the package maintainer to get up in the middle of his/her sleep just to answer your question isn't either. If you read the ?geary.test, you would see that you require a single variable, so analyse each of your columns in turn. You have a weights matrix, but geary.test() needs a listw object, so use mat2listw() to construct it. RSiteSearch() on Geary test takes you directly to the function you need, but for listw matrix the hits are a bit more diffuse. Roger Bivand
Using the above 2 matrices, I am trying to compute the Geary's *C* statistic for each of the *p* dimensions and also obtain corresponding *p*-values to determine its statistical significance for spatial autocorrelation. I will appreciate any help you could provide me in helping me compute the same. Thanks.