[R-sig-Geo] about ST kriging

[Edzer Pebesma]

Pinar, what are the dimensions (space and time) of your data, i.e. what
does dim(w) return?

Have you tried kriging with a (spatial and/or temporal) subset?

On 09/22/2011 01:38 PM, Pınar Aslantas Bostan wrote:
> Hi Edzer,
> 
> Thank you very much for your mail. I found two records have identical location, but it is not my fault because I checked the original source data and it is erroneous. 
> 
> Now I have another problem; R gives another error message:
> Error: cannot allocate vector of size 95.4 Mb
> 
> My computer includes 32-bit Windows and  3,5 GB RAM. I am not sure if I install 64-bit Windows, then the problem is solved? Or maybe I should minimize the data. Do you have any idea about it?
> 
> Best wishes,
> Pinar
> 
> -----Original Message-----
> From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Edzer Pebesma
> Sent: Wednesday, September 21, 2011 3:46 PM
> To: r-sig-geo at r-project.org
> Subject: Re: [R-sig-Geo] about ST kriging
> 
> Hi Pinar,
> 
> it is not clear which variogram model you pass, or how your data are
> laid out in space and time.
> 
> Possible causes for a non-positive definite covariance matrix include:
> 
> - a variogram model with (nearly) perfect correlation
> - duplicate observations (observations having identical location AND time)
> - an invalid variogram model
> 
> A small, reproducible example (data + script) would help identify the
> problem.
> 
> Best regards,
> --
> Edzer
> 
> On 09/20/2011 11:15 AM, Pınar Aslantas Bostan wrote:
>> Dear all,
>>
>> I am working about space-time kriging. Before I asked again about ST kriging
>> but now the problem is 
>> different and I could not overcome it!
>>
>> During kriging operation I got this error:
>>
>>> pred = krigeST(prec~1, w, STS(grid,time,index), v)
>> Error in chol.default(A$Sm, LINPACK = TRUE) : 
>>   non-positive definite matrix in 'chol'
>>
>> I explained the data set below:
>>
>> # prec is annual precipitation measured from 257 meteorological stations
>>
>> # w is STSDF object
>>> summary(w)
>> Object of class STSDF
>> [[Spatial:]]
>> Object of class SpatialPoints
>> Coordinates:
>>          min     max
>> Xnew  140556 1730472
>> Ynew 4309064 4971309
>> Is projected: NA 
>> proj4string : [NA]
>> Number of points: 257
>> [[Temporal:]]
>>      Index                      object at time  
>>  Min.   :1970-01-01 12:00:00   Min.   : 1.0  
>>  1st Qu.:1979-07-03 00:00:00   1st Qu.:10.5  
>>  Median :1989-01-01 12:00:00   Median :20.0  
>>  Mean   :1989-01-01 02:46:09   Mean   :20.0  
>>  3rd Qu.:1998-07-03 00:00:00   3rd Qu.:29.5  
>>  Max.   :2008-01-01 12:00:00   Max.   :39.0  
>> [[Data attributes:]]
>>    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
>>   114.5   413.7   533.6   633.0   735.6  3332.0 
>>
>> # I used grid to obtain predictions over it. It has 25 km spatial resolution
>>
>> # time is temporal entity of study. It contains 39 annual observation.
>>
>> # index is required for STSDF, and I used this code to create index.
>>> index <- cbind(as.integer(as.factor(data$Station)),
>> as.integer(as.factor(data$Year)))
>>
>> # v is space-time variogram
>>
>> How can I solve the problem?
>> Thank you in advance!
>>
>>
>> Pinar Aslantas Bostan
>> Research Assistant
>> Department of Geodetic and
>> Geographic Information Technologies (GGIT) Middle East Technical University
>> 06531 Ankara/TURKEY
>> aslantas at metu.edu.tr
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at r-project.org
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> 

-- 
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