Munroe, Darla K
Thu, 15 Apr 2004 09:17:33 -0700
Hello, >From experience, I am somewhat suspicious of the Delaunay triangulation routine in the Matlab Spatial Econometrics Toolbox. I'm tried to replicate matrices that I calculated with the simplest of datasets (i.e., a raster grid), and not gotten the same results. If you are using Matlab to do your modeling, it's definitely the best that's out there, but there are some other tools available. In particular, there is Luc Anselin's GeoDa package, which is free. It's still in beta format, but the final release will be sometime this fall. It's really a wonderful package for all sorts of data exploration and spatial data exploration. It can handle tens of thousands of obs (which SpaceStat couldn't), and it can create all sorts of weights matrix, as well as estimate a couple spatial regression models: http://sal.agecon.uiuc.edu/geoda_main.php - DM -----Original Message----- From: Mark Coleman [mailto:[EMAIL PROTECTED] Sent: Thursday, April 15, 2004 9:42 AM To: [EMAIL PROTECTED] Subject: AI-GEOSTATS: "Naive" question on lat-long conventions Greetings, I apologize in advance for what must be a rather naive question, but I am new to the field of spatial statistics. In the course of learning and testing various estimation methods with test data sets, I have a couple of questions regarding conventions regarding lat-long coordinates. In particular, I have been using a small test data set provided by Anselin on crime data in Columbus OH. Each sample point includes a lat-long coordinate. The data set can be found at http://www.spatial-econometrics.com/data/ As an example, the first point in this data set shows latitude=35.62, longitude=42.38. Yet when I check the coordinates of a random point in Columbus OH (not in the dataset), I find coordinates in the range of Lat=40.x, Long= -82.y. I use the points in the Anselin data set to calculate a spatial distance matrix using Delaunay Triangulization. I wanted to be sure that I understand what the conventions are when encoding lat-long coordinates. In the end, I need to understand this so I can calculate the distance between two points based on their lat-long coordinates. Thanks, Mark -- * To post a message to the list, send it to [EMAIL PROTECTED] * As a general service to the users, please remember to post a summary of any useful responses to your questions. * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list * Support to the list is provided at http://www.ai-geostats.org -- * To post a message to the list, send it to [EMAIL PROTECTED] * As a general service to the users, please remember to post a summary of any useful responses to your questions. * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list * Support to the list is provided at http://www.ai-geostats.org