[R-sig-Geo] Error gstat function krigeST

[Edzer Pebesma]

On 08/04/2014 04:38 PM, Francesco Tonini wrote:
> Dear Dr. Pebesma,
> 
> The exponential ST variogram did not solve the error. However, I 
> manually set the lower bound for the nugget parameter to be equal to 1 
> for both space and time. Even though the automatic optim() routine would 
> estimate these to be 0, I decided to add a nugget variance to avoid the 
> matrix singularity issue you mentioned. I am not sure why it would 
> estimate a nugget of 0 (=no measurement error) on my data. Any idea why 
> this could be?
> 
> Once I manually add a nugget variance, I now get this error when running 
> the krigeST():
> 
> Error in cbind(v0, X) : number of rows of matrices must match (see arg 2)
> 
> The parameters of this krigeST function are unchanged, and the only 
> thing that is modified is the variogram model described above.
> 
> Any help is much appreciated.

As usual: a small, reproducible example might help; if data are large,
please send them off-list.


> 
> Thank you,
> Francesco
> 
> 
> 
> 
> On 8/3/2014 5:14 AM, Edzer Pebesma 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
>>>
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>>
>>
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> 
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-- 
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

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