Digby That is the 'traditional' cross semi-variogram as discussed in Matheron's original work. Now also known as a co-located cross semi-variogram.
There is a non-co-located cross semi-variogram which goes something like: gamma(h)=1/2N(h) SUMi,j(vi-uj)^2 which is always positive. However, you probably have to standardise u and v to get meaningful results (which you can't really do with skewed data). Noel Cressie has shown in a paper in Math Geol that a semi-variogram calculated on logarithms is the same generically as a general relative semi-variogram. I should think that conclusion probably holds for cross semi-variograms too. Calculating on logarithms is computationally simpler than calculating a relative semi-variogram. Isobel Clark http://uk.geocities.com/drisobelclark --- Digby Millikan <[EMAIL PROTECTED]> wrote: > Hello everyone, > The forumlea which I have obtained for the cross > variogram is; > > gamma(h)=1/2N(h) SUMi,j(vi-vj)(ui-uj) > > Is it correct then that the product of the > differences can be negative in > cases. > > Digby __________________________________________________ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com -- * 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
