[R-sig-Geo] Spacetime regression

[Edzer Pebesma]

On 02/13/2014 01:30 PM, Roelof Coster wrote:
> Hi all,
> 
> I want to do a spatio-temporal regression on a quite large dataset. I have
>> 100 k records. These correspond to measurements taken at 3000 locations,
> approximately every half year. The geographic area is all of the
> Netherlands (240 x 300 km).

Sample variograms are a quadratic form, meaning that all pairs of your
100K records are evaluated; that makes 10^10 pairs. Are you a patient
person?

> Is spatio-temporal kriging advisable for a dataset that is so large?
> 
> When I make the sample space-time variogram (with variogramST), it
> automatically chooses a time-lag difference of about 2 days. This is much
> too small to be meaningful for my data; half-year periods would be
> interesting. Is there a way to tell this to the variogramST function?

variogramST (in package gstat) assumes that the time gap between
observations is constant. If you have "approximately every half year"
observations, are some of them only a few days apart? Did you see a
warning printed?

If the time differences are very un-even, the whole activity may be
pretty meaningless (with current implementation), and a mapping to
stricter regularity might help. We have coding Friday tomorrow, drop by
or send something useful and we might be able to work it out.
-- 
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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