R help - Sep 2010 - Linear models (lme4) - basic question

Hi,

Sorry for a basic questions on linear models.

I am trying to adjust raw data for both fixed and mixed effects. The data that I
output should account for these effects, so that I can use the adjusted data for
further analysis.

For example, if I have the blood sugar levels for 30 patients, and I know that 
'weight' is a fixed effect and that 'height' is a random effect,
what I'd want
as output is blood sugar levels that have been adjusted for these effects. 


===================library("lme4")
sugar <- c(1:10,sample(1:100,20))
weight <- 1:30
height <- rep(sample(1:15,15,replace=F),2)

lm.adj <- lmer(sugar ~ weight + (1|height))

adjusted.sugar <- fitted(lm.adj)

====================
I'm not sure if I'm doing this right...?

thanks!



      
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Why should height be a random effect?

I suspect you may need a tutorial on what a random effect in a mixed
model is. I see no obvious reason why one would cluster on height.
Perhaps if you clarify, it may become obvious either what your
concerns are (and that your model is correct) or that you
misunderstand and need a tutorial on random effects in mixed models.
Some kind soul on this list may provide that (not me, though) -- or
you can talk with your local statistician.

Cheers,
Bert

On Thu, Sep 2, 2010 at 9:22 AM, James Nead <james_nead at yahoo.com>
wrote:
> Hi,
>
> Sorry for a basic questions on linear models.
>
> I am trying to adjust raw data for both fixed and mixed effects. The data
that I
> output should account for these effects, so that I can use the adjusted
data for
> further analysis.
>
> For example, if I have the blood sugar levels for 30 patients, and I know
that
> 'weight' is a fixed effect and that 'height' is a random
effect, what I'd want
> as output is blood sugar levels that have been adjusted for these effects.
>
>
> ===================> library("lme4")
> sugar <- c(1:10,sample(1:100,20))
> weight <- 1:30
> height <- rep(sample(1:15,15,replace=F),2)
>
> lm.adj <- lmer(sugar ~ weight + (1|height))
>
> adjusted.sugar <- fitted(lm.adj)
>
> ====================>
> I'm not sure if I'm doing this right...?
>
> thanks!
>
>
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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