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re: st: repeated (sic) longitudinal analysis

From   "Airey, David C" <david.airey@Vanderbilt.Edu>
To   "" <>
Subject   re: st: repeated (sic) longitudinal analysis
Date   Wed, 8 Sep 2010 15:12:10 -0500


I think -xtgee- only allows one level of repeated measures data, not more. If you have multilevel data, you need to use mixed models, such as -xtmixed-.


> Dear all,
> I am analysing the following study :
> - healthy subjects are eating a meal ad libitum and the quantity of food (number of forks for example) is recorded every minute : energy, glucids, lipids and proteins
> - the meal is repeated 3 times in 2-4 weeks : once fasted (meal 0) and twice not fasted (meals 1 & 2).
> Usually I use xtgee to do longitudinal analyses when subjects are different, something like :
> xtset id_subject minute
> xi: xtgee kcal i.meal, family(gaussian) link(identity) corr(exchangeable)
> But this time the same subject eats the three meals and I want to know if the three curves are different in their shape (besides the AUC, slopes...).
> Do you have any idea how to include in the GEE model the fact that it is the same subject who is re-recorded to take into account this variability ?
> It sounds to me like clusters but I didn't find how to put it in the GEE model. I had also a look at gllamm but I am not familiar with it.
> Thanks for your help. Best regards,
> Hubert

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