[R] lme model specification

[Eric Hack]

Thanks for the response.  It is actually a repeated measures study, I
just mention the fixed effects specification because I think I know the
random effect specification, i.e.:
Random = ~ 1|subject

And thanks for the tip about the nonlinear model and the S-plus list.  I
will check out nlme and the other list.

Eric

On 6/9/05, Eric Hack <hack at tera.org> wrote:
> Dear All,
> 
> 
> 
> I am trying to specify the following fixed effects model for lme:

If you have a linear fixed-effects model you should use lm, not lme.

> 
> y ~ constant1 - beta1*(x - beta2)
> 
> where y is the response, x is the independent variable, and the
> operators above are real arithmetic operations of addition,
subtraction,
> and multiplication.  I realize that this model is just a
> reparameterization of y=beta0+beta1*x, but I am using this
> parameterization because I am specifically interested in confidence
> bounds for beta2.

You would need to fit that as a nonlinear model.  In reference to such
models "linear" means "linear in the parameters" and that model isn't.

 
> I have looked at the help, but the closest hint I find is the I()
> function, and that does not seem to work this way.
> 
> 
> 
> I confess that I am actually using S-plus, but there does not seem to
be
> a resource like this list for S-plus.

Look for the S-news email list (http://www.biostat.wustl.edu/s-news/)