Hi Chris, The back transform of simulated values is very easy to perform. Just take the exponential of the simulated values since you are not trying to estimate the mean of the local probability distribution in the original space, but only a quantile of this distribution. Note that if you perform SGS using Gslib, there is a built-in normal score transform and back-transform in the program, which is more flexible than the lognormal transform.
Cheers, Pierre <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> Dr. Pierre Goovaerts President of PGeostat, LLC Chief Scientist with Biomedware Inc. 710 Ridgemont Lane Ann Arbor, Michigan, 48103-1535, U.S.A. E-mail: [EMAIL PROTECTED] Phone: (734) 668-9900 Fax: (734) 668-7788 http://alumni.engin.umich.edu/~goovaert/ <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> On Fri, 17 Oct 2003, Chris Lloyd wrote: > Hello, > > The subject of logs and back transforms has been discussed a great deal > on the list and I've seen much material concerning back transforms > following kriging of log transformed data (e.g., the approach outlined > by Cressie in his book 'Statistics for Spatial Data' and many other > texts). However, I am unsure how to proceed if the objective is > simulation. > > I have applied sequential Gaussian simulation to log (base 10) > permeability data and I want to back transform the simulated > realisations. I would be grateful for any suggests from list members as > to how best to back transform the values in this case. There are too few > data to make an indicator approach feasible. > > I will post a summary of answers. Many thanks in advance. > > Chris Lloyd > > > -- * 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
