[STATSGRASS] gstat: problem with prediction value at point location

[Jarek Jasiewicz]

Roger Bivand napisa?(a):
> On Tue, 23 Jan 2007, [UTF-8] Jarosław Jasiewicz wrote:
>
>   
>> Roger Bivand napisał(a):
>>     
>>> On Tue, 23 Jan 2007, Edzer J. Pebesma wrote:
>>>
>>>   
>>>       
>>>> My guess is that the technique you're referring to (and used by 
>>>> Geostatistical Analyst, afaik) is [kriging in] cross 
>>>> validation---observations are left out to obtain a kriging estimate for 
>>>> which it makes sense to compare it with the observation. Definitely 
>>>> distinct from kriging, which does not leave observations out.
>>>>     
>>>>         
>>> When run head to head, gstat CV LOO (leave one out) on trend surfaces and 
>>> GA give the same results, so, yes, GA seems by default to do LOO CV.
>>>       
>
> Leave-one-out cross validation is when you make a prediction for data 
> point j, using the data for point i=1,...,n; i!=j (leave out j). That 
> means that you can validly compare the observed value at j with its 
> prediction made using all the rest of the data (and the same variogram 
> model for all cases). Then you do RMSE on the LOO CV residuals. See 
> ?gstat.cv in the gstat package.
>
> Roger
>
>   
>>> Roger
>>>
>>>   
>>>       
>> Sorry I didn't uderstand that...
>> Jarek
>>
>>     
>
>   
thanks, all clear
reagrds
Jarek