Hello,

There are no duplicate times nor coordinates in my dataset. I do not have this type of error when aggregating the dataset to daily observations. I suspect it could also be because the estimated nugget parameters, when working at hourly resolution, for both space and time in my ST variogram are set to 0...could it be that? I'm trying to fill all missing value gaps in my dataset and not predict on a grid. I am predicting over the same observations using a cross validation method.

Thanks,
Francesco



Sent from my iPhone

> On Aug 3, 2014, at 5:14 AM, Edzer Pebesma <edzer.pebesma@uni-muenster.de> wrote:
> 
> Dear Francesco, there are several reasons why this could happen. The
> first one I would look at is whether you have duplicate observations,
> meaning observations that share exactly the same spatial and temporal
> coordinate. Let me know if it helped,
> 
>> On 07/31/2014 05:45 PM, Francesco Tonini wrote:
>> Dear all,
>> 
>> I am working with an hourly dataset of air temperature, recorded at ~200
>> stations over a relatively small area. I chose a space-time variogram
>> (e.g. sum-metric) to fit my data and am now trying to make predictions
>> over my same stations in order to fill NA (missing value) gaps. When
>> using the krigeST() function over daily aggregated data everything seems
>> to go smooth but when I use it at the original hourly resolution I
>> always get the following error:
>> 
>> Error in chol.default(A)
>> the leading minor of order 68 is not positive definite
>> 
>> I googled it and found that it is related to a matrix not being
>> completely positive-definite. However, I am not sure why this happens
>> and was wondering if any of you know a way of fixing this (a workaround
>> to avoid it).
>> 
>> Thanks!
>> Francesco
>> 
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo@r-project.org
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> 
> -- 
> Edzer Pebesma
> Institute for Geoinformatics (ifgi), University of Münster
> Heisenbergstraße 2, 48149 Münster, Germany. Phone: +49 251
> 83 33081 http://ifgi.uni-muenster.deGPG key ID 0xAC227795
> 
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo

Sent from my iPhone

> On Aug 3, 2014, at 5:14 AM, Edzer Pebesma <edzer.pebesma@uni-muenster.de> wrote:
> 
> Dear Francesco, there are several reasons why this could happen. The
> first one I would look at is whether you have duplicate observations,
> meaning observations that share exactly the same spatial and temporal
> coordinate. Let me know if it helped,
> 
>> On 07/31/2014 05:45 PM, Francesco Tonini wrote:
>> Dear all,
>> 
>> I am working with an hourly dataset of air temperature, recorded at ~200
>> stations over a relatively small area. I chose a space-time variogram
>> (e.g. sum-metric) to fit my data and am now trying to make predictions
>> over my same stations in order to fill NA (missing value) gaps. When
>> using the krigeST() function over daily aggregated data everything seems
>> to go smooth but when I use it at the original hourly resolution I
>> always get the following error:
>> 
>> Error in chol.default(A)
>> the leading minor of order 68 is not positive definite
>> 
>> I googled it and found that it is related to a matrix not being
>> completely positive-definite. However, I am not sure why this happens
>> and was wondering if any of you know a way of fixing this (a workaround
>> to avoid it).
>> 
>> Thanks!
>> Francesco
>> 
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo@r-project.org
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> 
> -- 
> Edzer Pebesma
> Institute for Geoinformatics (ifgi), University of Münster
> Heisenbergstraße 2, 48149 Münster, Germany. Phone: +49 251
> 83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795
> 
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo

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