[R-sig-Geo] Co-Kriging with huge data

[Kai Zhang]

Hi Edzer,

Thanks for your reply. I am not sure if I get your point -- "Maybe a cross validation with your 17 temperature monitors can give you
some idea on this". I am wondering if you mean sensitivity analysis of neighbor size using cross-validation. For example, based on 17 monitors, I could try the radius with 1 km, 2 km and so on using cross-validation and choose a neighbor size with smallest RMSE calculated from cross validation.

I appreciate your response and best regards,
Kai

____________________________________________________
Kai Zhang
PhD Candidate, Environmental Health Sciences
School of Public Health                        
University of Michigan                         
109 S. Observatory                       
Ann Arbor, MI 48109-2029         
____________________________________________________

======= 2009-12-14 02:49:22 You wrote =======

>
>
>Kai Zhang wrote:
>> Dear all,
>>
>> I have temperature measurements at 17 monitors.  I have a secondary variable across the study area, which includes 230,000 points. I tried to conduct Co-Kring with this huge dataset and it appeared to be computationally intensive. Is there any way to run it except for running the program in a cluster?
>>
>> I appreciate your response and best regards,
>> Kai
>>   
>One alternative would be to use co-kriging and to limit the search
>neighbourhood for the secondary variable. The question is how much.
>Maybe a cross validation with your 17 temperature monitors can give you
>some idea on this. If someone knows about existing literature on this,
>I'd be happy to hear.
>
>Another possibility is to use universal kriging, with your secondary
>variable treated as predictor. For this, you need the values of your
>secondary variable to be known ath the 17 monitor sites, and the
>prediction locations should coincide with (some of) the 230000 points.
>It is not equivalent to the first approach, poorer in the sense that it
>ignores the secondary variable at locations beyond the prediction
>location, but assumes a linear relationship between the two as well.
>
>-- 
>
>Edzer Pebesma
>Institute for Geoinformatics (ifgi), University of Münster 
>Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251 
>8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de 
>http://www.52north.org/geostatistics      e.pebesma at wwu.de
>