hot spot analysis - variables with positive and negative values

[JosefBernard]

Hi,
I would like to use the hot spot analysis Getis Ord Gi for detecting spatial clusters of rural development potentials.
I use factor scores resulting from factor analysis as development indicators, hence their values are both positive and negative. Are results of the hot spot analysis valid even for variables with negative values? Getis Ord general G works only with positive values. The hot spot analysis gives me interesting results with my variables, but is it statistically OK?

Thank you for your answer.

Josef Bernard

[LaurenRosenshein]

Hi Josef,

That's a great question! 

You absolutely can trust the results of your Hot Spot Analysis (Getis-Ord Gi*) on data with negative values.  The Getis-Ord Gi* statistic that is implemented in ArcGIS is based on the 1995 paper by Getis and Ord (Ord, J.K. and Arthur Getis. 1995. "Local Spatial Autocorrelation Statistics." _Geographical Analysis_ 27(4): 287-306.).  The 1995 implementation absolutely DOES allow for negative values, so you can go ahead and feel confident in the results that you're getting. 

Hope this helps!

Lauren Rosenshein
Geoprocessing Product Engineer