variogram estimation with adaptive sampling weights
Hi John, I recently wrote a variogram fitting routine using the R function optim(). It works together with gstat. It is quite straightforward to write you own goal function for optim(), including the weights to use in the fitting. Send me an e-mail offlist if you need the code and some examples. cheers, Paul
Carson, John wrote:
Dear r-sig-geostat members, I have a spatial soil sampling design which will be used for a moderately large number of areas. The first or primary stage is systematic. Any primary locations observed to exceed one or more thresholds (it's a multivariable problem) will trigger (composite) sample collection in the 4 adjacent grid areas. So the sampling is adaptive cluster sampling, and I use sampling weights for Horvitz-Thompson estimation (prop to 1/(prob of selection)). I know that variograms estimated with this kind of clustered data can be biased. I would like to directly incorporate sampling weights into the variogram estimation. I have used gstat and geoR previously and don't see an easy way to use external weights. Does anyone know how to use external weights for variogram estimation in these packages? Or are there other libraries that would work better? Thanks in advance, John John H. Carson Jr., PhD Senior Statistician Applied Sciences & Engineering Shaw Environmental & Infrastructure 16406 US Rte 224 East Findlay, OH 45840 Phone 419-425-6156 Fax 419-425-6085 john.carson at shawgrp.com http://www.shawgrp.com/ <http://www.shawgrp.com/> Shaw(tm) a world of Solutions(tm) <http://www.shawgrp.com/> To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey ****Internet Email Confidentiality Footer**** Privileged/Confidential Information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such case, you should destroy this message and notify the sender by reply email. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of The Shaw Group Inc. or its subsidiaries shall be understood as neither given nor endorsed by it.
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Drs. Paul Hiemstra Department of Physical Geography Faculty of Geosciences University of Utrecht Heidelberglaan 2 P.O. Box 80.115 3508 TC Utrecht Phone: +3130 274 3113 Mon-Tue Phone: +3130 253 5773 Wed-Fri http://intamap.geo.uu.nl/~paul