about ST kriging
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, P?nar 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
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Edzer Pebesma Institute for Geoinformatics (ifgi), University of M?nster Weseler Stra?e 253, 48151 M?nster, Germany. Phone: +49 251 8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de http://www.52north.org/geostatistics e.pebesma at wwu.de _______________________________________________ R-sig-Geo mailing list R-sig-Geo at r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo