Hey I would be really appreciative if anyone can help me out with a problem I am having with the GWR tool. The GWR works fine when I run it on a particular shapefile. However I want to run a GWR where I need to add a field to the shapefile, and that is where the problem occurs. The original shapefile has fields for homicide rate in the United States in 1970 and 1980. I want to create a new field that has change in homicide rate between 1970 and 1980. To do this I just create a new field and use the field calculator to subtract the 1970 field from the 1980 field. Now when I try and run the GWR with this new field is my dependent variable I get an error. The error is something involving not having enough data to run the GWR. After I create the new field this error comes up every time, even when I don't use the newly created field as the dependent variable. Something happens when I create this new field so that the GWR no longer works for the entire dataset. Does anyone have any idea what is going on here? Any help would be very much appreciated. Thank you!!!