Parameter restrictions

Dear all,

is there a simple way in R to add parameter restrictions to linear mixed effects models. Specifically I would like to restrict a slope coefficient to be equal to 1.

That is done by adding an offset, which can be done in two ways.  The
general model might be

lmer(y ~ 1 + x + (1|g))

and the model with the slope restricted to 1 is either

lmer(y ~ 1 + offset(x) + (1|g))

or

lmer(y ~ 1 + (1|g), offset=x)

IIRC one of them works properly and one doesn't although I can't
recall which one is which.  Try them both.