## AI-GEOSTATS: cross-validation

Expand Messages
• Dear list members My question is as folows: For a variable after getting a number of models all of which seem well, how to decide which one is the best among
Message 1 of 3 , Mar 25, 2002
Dear list members

My question is as folows:

For a variable after getting a number of models all of
which seem well, how to decide which one is the best
among them based on cross-validation results.
i.e., How to use cross-validation results of a model
to compare with those of others?

Best regards
Ercan Yesilirmak

__________________________________________________
Do You Yahoo!?
Yahoo! Movies - coverage of the 74th Academy Awards�
http://movies.yahoo.com/

--
* To post a message to the list, send it to ai-geostats@...
* As a general service to the users, please remember to post a summary of any useful responses to your questions.
* To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
* Support to the list is provided at http://www.ai-geostats.org
• Dear Ercan Cross validation could for example be performed by discarding a single observation from the dataset and predicting this single observation based on
Message 2 of 3 , Mar 26, 2002
Dear Ercan

Cross validation could for example be performed by discarding a single
observation from the dataset and predicting this single observation based on
the rest of the dataset and with the proposed model. This is repeated for all
the observations in the dataset, and as a measure of the goodness of the model
you could calculate

GOM = sum[(observation - predicted)^2]/n

If you have n observations this procedure is referred to as n-fold cross
validation. Altenatively you could split your dataset into 10 parts,
then discarding one part and predicting this part based on the other 9
parts and the proposed model, would give you 10-fold cross validation.

If you want to compare different models, off course the one which gives
the lowest GOM - value is the best for predicting the variable.

Best regards / Venlig hilsen

Søren Lophaven
******************************************************************************
Master of Science in Engineering | Ph.D. student
Informatics and Mathematical Modelling | Building 321, Room 011
Technical University of Denmark | 2800 kgs. Lyngby, Denmark
E-mail: snl@... | http://www.imm.dtu.dk/~snl
Telephone: +45 45253419 |
******************************************************************************

On Mon, 25 Mar 2002, Ercan Yesilirmak wrote:

> Dear list members
>
> My question is as folows:
>
> For a variable after getting a number of models all of
> which seem well, how to decide which one is the best
> among them based on cross-validation results.
> i.e., How to use cross-validation results of a model
> to compare with those of others?
>
> Best regards
> Ercan Yesilirmak
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Movies - coverage of the 74th Academy Awards®
> http://movies.yahoo.com/
>
> --
> * To post a message to the list, send it to ai-geostats@...
> * As a general service to the users, please remember to post a summary of any useful responses to your questions.
> * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
> * Support to the list is provided at http://www.ai-geostats.org
>

--
* To post a message to the list, send it to ai-geostats@...
* As a general service to the users, please remember to post a summary of any useful responses to your questions.
* To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
* Support to the list is provided at http://www.ai-geostats.org
• Dear all, Question is about evaluation of cross-validation results (MSE), performed as part of kriging/cokriging interpolation on different oil fields. Does
Message 3 of 3 , Nov 26, 2003
Dear all,

Question is about evaluation of cross-validation results (MSE), performed as
part of kriging/cokriging interpolation on different oil fields.

Does anybody have experience with comparing of different MSE values in
similar lithofacies? Is it necessary to have (for comparison) same number of
wells/data in each lithofacies or it can differ in some range?

Maybe somebody knows for papers/tables where absolute MSE values (regarding
interpolation method, number of data and analysed facies) and their meaning
are published.

Best regards,

Tomislav Malvic, INA oil company, Croatia

--
* To post a message to the list, send it to ai-geostats@...
* As a general service to the users, please remember to post a summary of any useful responses to your questions.
* To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
* Support to the list is provided at http://www.ai-geostats.org
Your message has been successfully submitted and would be delivered to recipients shortly.