Dear Gregoire,
Still, part of the question remained unanswered. We all agree that in
The real issue was however the fact that the investigated dataset was
not considered to present a pure nugget efffect!
What are thus the requirements for not observing this decrease and how
Dear Gregoire,
I just recently read your original question. I've not read all the
replies since, so I hope what I say is not redundant or repetitive.
The phenomenon you are seeing is due to the smoothing effect of
kriging. This effect increases with geographic distance of estimates
from
Dear list,
I received a few more replies from Jon Skoien, Gerald van den Boogaart,
Denis Marcotte and Yücel Tandoğdu, to my question on the correlation
between kriging residuals and my input data. So many thanks to all for
the replies that all go in the same direction (please send your replies
Hi Gregoire
If I have understood the problem, the weird thing is that if there is
a strong correlation between data and residuals and your data show
continuity, the residuals should not present a pure nugget effect.
Sebastiano T.
At 12.59 30/01/2008, Gregoire Dubois wrote:
Dear list,
Dear list,
Having fit a variogram to a dataset (indoor radon measurements) and
applied cross-validations, I noticed the perfect negative correlation
(-0.95) between my kriging residuals and my input data.
This means that I am overestimating as much the low values as I am
underestimating the
Bob
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Gregoire Dubois
Sent: Wednesday, January 30, 2008 05:00
To: ai-geostats@jrc.it
Subject: AI-GEOSTATS: Correlation between kriging residuals and input data
Dear list,
Having fit a variogram to a dataset (indoor radon
-GEOSTATS: Correlation between kriging residuals and
input data
Gregoire,
If you interpolate with a pure nugget effect, this is what you would
expect for cross validation residuals because the predictions are
constant, except that usually the residuals are defined as (observed -
predicted) which
Lakewood, Co 80228
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Gregoire Dubois
Sent: Wednesday, January 30, 2008 05:00
To: ai-geostats@jrc.it
Subject: AI-GEOSTATS: Correlation between kriging residuals and input data
Dear list,
Having fit a variogram to a dataset (indoor
an official position of the
European Commission.
-Original Message-
From: Edzer Pebesma [mailto:[EMAIL PROTECTED]
Sent: 30 January 2008 14:13
To: Gregoire Dubois
Cc: ai-geostats@jrc.it
Subject: Re: AI-GEOSTATS: Correlation between kriging residuals and
input data
Gregoire,
If you interpolate
Dear Gregoire
As one who has dealt extensively with radon (but not from the
statistical world), I would appreciate it if you could post to one of
your sites either histogram in either log or some other plot. (or
your data if possible)
I have been dealing with over 50,000 data points
Hello Gregoire, and list,
I'd guess that, although you may be seeing some spatial structure in your
data, the effective range of your model may be less than the minimum distance
between the locations you are predicting and their closest known locations.
In other words, your model may
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