[R-sig-Geo] cokriging question

[Chris Taylor]

Good morning Edzer and Dave,
Thanks for bringing up this point.  I had a similar issue recently using 
krige().  Observations at 5800 locations, attempting to krige() 
predictions at 112,000 locations resulted in the same "memory.c" error 
message.  Reducing predicted locations to <<50,000 and reducing max.dist 
seemed to help, but the predictions still took a very long time (>2 
hours).  (Running winxp with 4GB memory.)
Can you clarify your suspicion regarding the "lack of standardization of 
coordinates"?

Chris

Edzer Pebesma wrote:
> Dave,
>
> 12000 observations fit, in the c representation, in less than 1 Mb (64 
> bytes per observation).
>
> The issue is that you think that passing maxdist to predict.gstat has 
> an effect. It doesn't; you need to pass it to function gstat().
>
> The same thing happened in this
> https://stat.ethz.ch/pipermail/r-sig-geo/2008-September/004182.html
> message, where nmax was passed to predict.gstat, and simulation took 
> forever. The other issue in that question was, I suspect, lack of 
> standardization of coordinates, used in a trend surface.
> -- 
> Edzer
>
> Dave Depew wrote:
>> Is there a limit to the # of observations or size of file that can be 
>> co-kriged in gstat?
>> I have a ~12000 observation data set (2 variables), the variograms, 
>> cross variogram and lmc are fit well, and co-kriging starts ok
>>
>> Linear Model of Coregionalization found. Good.
>> [using ordinary cokriging]
>>
>> then immediately outputs
>>
>> "memory.c", line 57: can't allocate memory in function m_get()
>> Error in predict.gstat(fit.ck, newdata = EcoSAV.grid, maxdist = 100) :
>>  m_get
>>
>> Iv tried different maxdist from 10 to 1000, with exactly the same 
>> result.
>> I recently upgraded my RAM to 4Gb and flipped the windows XP /3GB 
>> switch.
>>
>>
>

-- 
J. Christopher Taylor, Ph.D.
Applied Ecology and Restoration Research
National Ocean Service / NOAA  
National Centers for Coastal Ocean Science  
Center for Coastal Fisheries and Habitat Research  
101 Pivers Island Road, Beaufort, North Carolina 28516-9722  
Ph:(252) 838 0833  Fx:(252) 728 8784  
Website: http://www.ccfhr.noaa.gov/

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