some problems with krigeST

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Dear all,

I'm a newer to spatio-temporal analysis though I am quite familiar
with spatial one. When coming to spatio-temoral prediction using
krigeST, I have some queries as follows:

1. it seems that the krigeST can only deal with data with full
layout format (e.g., STFDF class), however our data in practice,
which is often the case, come with sparse format (e.g., STSDF
class) because of different No. of samples in each time point or
missing values. Under this circumstance, I mean only with STSDF
class, what I can do if I still want to make spatio-temporal
prediction? just sort out a  STFDF format from the available data?
or else

please look at the development version of gstat at
https://r-forge.r-project.org/R/?group_id=378
and in particular demo(localKrigeST) -- we addressed this issue on a
hackaton three weeks ago, and you're welcome to test ;-)

2. I happened to see a replying email by Edzer to someone which
said krigeST was designed to exploit separaility of spatio-temporal
covariance models. If this is the case, what dose other types of
spatio-temporal variogram (e.g., productSum, sumMetric, and
simpleSumMetric) mean? Do them predict with a jiont spatio-temporal
covariance? if so, why one needs to specify purely spatial and
temporal variogram if the jiont spatio-temporal covariance is
specified?

This was true for the first incarnation of krigeST; now it supports
more ST variogram model classes, many of which are non-separable. Look
at (the examples of) ?vgmST to see how they work.

3. In terms of specification of arguments in vgmST, it seems to be
too subjective to specify arguments for varigram of space and time,
for example, time = vgm(1, "Exp", 1.5 * 3600 * 24)). How could I
know range, sill, or nugget for the varigram?

This is a modelling / inference question. I will not go any further
here than saying that this is not trivial. Some hints at what you can
do with gstat are found in the package vignette("st"). Please don't
complain about the lack of options, but write working and readable
code. If you would contribute it, we will include it and acknowledge you!

- -- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of M?nster
Heisenbergstra?e 2, 48149 M?nster, Germany. Phone: +49 251
83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAD3A77F1
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