Re: AI-GEOSTATS: mysterious kriging output

2004-03-09 Thread Monica Palaseanu-Lovejoy
Hi, I am working myself with pollution data in soils and i have very high values very close to very low values, and highly skewed distribution. I am more and more concerned with doing kriging on transformed data. This simply means we believe the data came from only one population. But what if

Re: AI-GEOSTATS: mysterious kriging output

2004-03-09 Thread Monica Palaseanu-Lovejoy
Hi Ruben, thanks so much for the references and especially the R routines i will look into it. This may really give some good answers to my data - once for all - i hope at least. I think we neglect in majority of cases to verify if the data come from one or 2 (or more) distributions

AI-GEOSTATS: Re: mixtures of populations

2004-03-09 Thread Isobel Clark
Hello All The common 'Normal Score' transform assumes one population. Transformations such as rank or logarithm do not assume one population. The best way to identify likely mixtures is with programs such as Peter MacDonald's Mix (cited in Ruben's email I think):

Re: AI-GEOSTATS: mysterious kriging output

2004-03-09 Thread Pierre Goovaerts
Hello, I agree that in many environmental datasets we could question the assumption of existence of a single population. Although there are ways to split the data into several populations, the key issue is that the study area needs also to be stratified into several populations. In some fields,

AI-GEOSTATS: Re: mixtures of populations

2004-03-09 Thread Isobel Clark
AH me, the English language slips away from me again. I said that the PRESENCE {pardon the capitals, no way to italicise email} of more than one population is indicated by the points of inflexion on the probability plot. Not that these were breakpoints between populations. Normal (or lognormal)