Hi I was investigating my data and it is possible to identifie areas of zeros on the outside limits of the distribution, so it can be possible to model the spatial behaviour in two steps.
My guess is that I can simple reduce the kriging area to leave the zero area out. My doubt is how to model boundaries. I'm sure this is a common problem, so if you can give me some references I'll look forward to find them. Thanks and regards EJ On Wed, 2002-10-02 at 19:33, Donald E. Myers wrote: > Adding a constant to all values will shift the distribution but will not > change its shape. If the fraction of zeros is large then you will likely > not have a lognormal distribution and hence taking logs may not solve > the problem. If you intend using kriging (after applying a log > transform) then you will have to worry about the bias correction when > you re-transform, to do that the theoretical solution requires > multivariate lognormality (univariate is not sufficient). > > You might want to look at the spatial pattern of the zeros, i.e., is it > plausible to separate the data set spatially and have most of the zeros > in only one region? > > Donald E. Myers > http://www.u.arizona.edu/~donaldm > > Ernesto Jardim wrote: > > >Hi > > > >I'm analysing fisheries data (number of fish caught per hour) and I have > >some 0 values. When I log-trans I have to translate the values by hading > >some value. > > > >My question is which value is the best ? is there any works about this ? > > > >I usually had 1 so that I get values between 0 and infinite (no negative > >value) but I have doubts about it. > > > >Regards > > > >EJ > > > > > > > > > >-- > >* 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 > > > > > -- * 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
