[R-sig-ME] How to fix the value of random intercepts (lmer/MCMCglmm)

[Jarrod Hadfield]

Hi Sam,

You could do this in MCMCglmm but it sounds like it might (possibly)  
be a bad idea. Could you give more details on how Y is actually  
obtained?

Cheers,

Jarrod


Quoting "PATRICK, Samantha" <spatrick at glos.ac.uk> on Mon, 25 Aug 2014  
15:16:27 +0000:

> Hi All
>
> I am fitting a basic linear regression, where I want to estimate a  
> single population intercept and slope.  In addition I am fitting  
> random intercepts and slopes such that:
>
> lmer (Y ~Intercept + Continuous Variable + (Continuous Variable  
> |Indiviudal Group))
>
> However the exact value of the individual group intercepts is known  
> from the data set.  The reasons for this are a little involved but  
> essentially Y is a cumulative total and so at the intercept I want  
> to fit the actual cumulative total at this point for each  
> individual.  It is important as the slope per individual needs to be  
> constrained to pass through the actual intercept per individual.
>
> So I want to fit this model, estimating the population intercept and  
> slope.  I then want to fix the individual group deviation from the  
> population intercept (random intercepts), and from this model  
> extract estimates of individual group random slopes.
>
> I have been unable to find any examples of fixing intercepts, unless  
> they are fixed as a constant.  Is it possible to code the model in  
> such a way? The model can be run in MCMCglmm or lmer  which ever  
> package would allow me to constrain the intercepts.
>
> Thanks
>
> Sam​
>
>
> Dr Samantha Patrick
> Research Fellow
> Biosciences QU116
> Francis Close Hall Campus
> University of Gloucestershire
> Cheltenham, GL50 4AZ, UK
>
> Research Associate: OxNav, University of Oxford
>
> ******From 1st August - 14th November 2014 I will be
> based in Montréal, which is 5 hours behind GMT  ******
>
> Tel: 07740 472 719
> Skype: sammy_patrick
> https://sites.google.com/site/samanthacpatrick/
>
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