Tips for unbalanced data:
Those who are interested should have a look at the Peter Congdon's bugs
programs at ftp:///www.wiley.co.uk/pub/books/congdon, especially program
8.1. Please qoute his work in your future work and publications as a
courtesy.
Al Erkanli
--On Friday, August 24, 2001 1:53 PM -0500 Asimina Mila
<[log in to unmask]> wrote:
> At 10:58 AM 4/20/00 -0300, Teresa Cristina Martins Dias wrote:
> Dear users
>
> I have the same request. Could I receive the answer too?
> Thanks
>
>> Dea Winbugs users,
>>
>> I would like to receive the answer the question: Unbalanced data in a
>> hierarchical model ( Gerdien Van Schaik ).
>>
>> Teresa Cristina
>> -----Mensagem original-----
>> De: Gerdien Van Schaik <[log in to unmask]>
>> Para: [log in to unmask] <[log in to unmask]>
>> Data: Thursday, August 23, 2001 4:39 PM
>> Assunto: Unbalanced data in a hierarchical model
>>
>>
>>> Dear Winbugs users,
>>>
>>> I am running a hierarchical model in Winbugs of testdata of farms within
>>> region within country. I have unbalanced data because I have a different
>>> number of farms per region and per country. Country 1 has 4 regions and
>>> 91, 97, 93, and 97 farms per region. Country 2 has 3 regions with 30
>>> farms in each region. I am interested in the region and country effect
>>> and therefore combined the two datasets.
>>> My datastructure is a rectangular array and looks as follows:
>>>
>>> ncows[,1,1] probpos[,1,1] ncows[,2,1] probpos[,2,1]
>>> ncows[,3,1] probpos[,3,1] ncows[,4,1] probpos[,4,1] ncows[,1,2]
>>> probpos[,1,2] ncows[,2,2] probpos[,2,2] ncows[,3,2]
>>> probpos[,3,2] ncows[,4,2] probpos[,4,2]
>>>
>>> with the data underneath the headings in columns.
>>>
>>> In my model the hierarchy is modeled with the arrays i (=farm), j
>>> (=region), and k (=country). See a sample of the model below.
>>>
>>> model;
>>> {
>>> for( i in 1 : 97 ) {
>>> for( j in 1 : 4 ) {
>>> for( k in 1 : 2 ) {
>>>
>>> AP[i , j , k] ~ dbin(probpos[i, j, k], ncows[i , j , k])
>>>
>>> }
>>> }
>>> }
>>> }
>>>
>>> However, to be able to run this model I had to make the data balanced by
>>> artificially creating 4 regions in every country and 97 farms in every
>>> region. I would rather not have to create extra data because I may
>>> introduce errors by doing so.
>>> Can anybody help me with an array or data-structure that would solve my
>>> problem with different numbers of regions per country and different
>>> number of farms per region? I would be very obliged.
>>>
>>> Gerdien van Schaik
>>>
>>> ***********************************************************************
>>> ****
>> ********
>>> Ms. Gerdien van Schaik, PhD
>>> Cornell University,
>>> College of Veterinary Medicine
>>> Department of Population Medicine and Diagnostic Sciences (box 26),
>>> Ithaca, NY, 14853,
>>> USA.
>>> ph. 607 253-4329
>>> fax 607 253-3083
>>> ***********************************************************************
>>> ****
>> ********
>>>
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>>
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>
> Asimina L. Mila
> Graduate Student - Research Assistant
> Plant Pathology Dept.
> 351 Bessey Hall
> Iowa State University
> Ames, IA 50011
> 515-294-3660
> [log in to unmask]
>
> -------------------------------------------------------------------
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>
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> [log in to unmask]
>
>
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