> To be a valid covariance function, it must be > positive definite (as a function). In particular > this implies that the function is bounded > (hence no polynomials) I hate to sound ignorant here, but aren't most of the standard semi-variogram models polynomials of one kind or another?
I remember seeing a paper a few years ago by a coupl eof blokes from Pretoria University on a generalised polynomial fit which would be positive definite. I don't have it to hand but can probably track it down if given sufficient motivation ;-) Isobel Clark http://geoecosse.bizland.com/news.html __________________________________________________ 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
