Re: [ai-geostats] Nugget effect...

2005-09-05 Thread Barrie Wells
Do you have non-spatial control data? i.e. have you measured resistivity at single locations at a number of frequencies? This should help show you whether the effect you are seeing on the spatial data set is due to uncreased accuracy with longer frequency (as suggested by Colin Badenhorst,

RE: [ai-geostats] natural neighbor applied to indicator transforms

2005-09-05 Thread Gregoire Dubois
Title: Message Ciao Sebastiano, I realized nobody replied to your question (sorry for have added confusion here). I don't see any objection in applying any interpolator to probability values. However, you should better use exact interpolators to avoid getting probabilities of

RE: [ai-geostats] natural neighbor applied to indicator transforms

2005-09-05 Thread Pierre Goovaerts
Hi, In fact, as long as the weights are all positive and sum up to one, your interpolated probability will always be between 0 and 1; so you should be all right.. The approach proposed by Sebastiano is similar to median indicator kriging in the sense that the weights assigned to the

RE: [ai-geostats] natural neighbor applied to indicator transforms

2005-09-05 Thread seba
Dear Pierre and Gregorie Thank you for your help . Concluding (considering that natural neighbor method should be a convex and an exact interpolator) it seems that the approach has not side effects !! Sincerely Sebastiano At 17.19 05/09/2005, you wrote: Content-Class:

[ai-geostats] back transformation

2005-09-05 Thread Recep kantarci
Dear list members Whenstudied on alog-transformed variable and intended toconstruct prediction intervals, whichoption should be followed? Why? 1) construct prediction interval first, back-transform later. OR 2) back-transform first, construct prediction interval later. Thanks in advance Recep

Re: [ai-geostats] back transformation

2005-09-05 Thread Isobel Clark
What back-transform would you use for (1)? I use Sichel's theory, which produces prediction intervals for the lognormal back transform. Download any one of my lognormal kriging papers from http://uk.geocities.com/drisobelclark/resume (late 1990s, various audiences). IsobelRecep kantarci [EMAIL