# fixing a parameter in lme4

#### Lazar

##### Phineas Packard
Say I have a model like:
Code:
lmer(y~x1 + x2 + x1:x2 + (1|id))
Say I want to fit this model and then for reasons that are not worth explaining here I want to refit the model where the fixed effects for x1 and x2 are fixed to some value say b_x1= .45 and b_x2 = .63. How would I go about doing this?

#### Lazar

##### Phineas Packard
hmm yeah. I saw offset fixes at 1 but the idea of:
Code:
I(offset(.45*x1) + I(offset(.63*x1))
might work?

#### TheEcologist

##### Global Moderator
hmm yeah. I saw offset fixes at 1 but the idea of:
Code:
I(offset(.45*x1) + I(offset(.63*x1))
might work?
Yes, I'd say it would.