[R] formula in fixed-effects part of GLMM

[Douglas Bates]

Henric Nilsson wrote:
> On Mon, 2005-05-02, 17:24, Douglas Bates wrote:
> 
> 
>>weihong wrote:
>>
>>>Can GLMM take formula derived from another object?
>>>
>>>foo <- glm (OVEN ~ h + h2, poisson, dataset)
>>>
>>># ok
>>>bar <- GLMM (OVEN ~ h + h2, poisson, dataset, random = list (yr = ~1))
>>>
>>>#error
>>>bar <- GLMM (foo$formula, poisson, dataset, random = list (yr = ~1))
>>>#Error in foo$("formula" + yr + 1) : invalid subscript type
>>
>>That won't work without some tweaking of the GLMM function.  In the
>>0.95-1 and later versions of the lme4 package the capabilities of GLMM
>>have been folded in to the lmer function and you would need to fit that
>>model as
>>
>> lmer(OVEN ~ h + h2 + (1|yr), dataset, poisson)
>>
>>anyway.
> 
> 
> I don't have access to the "White Book" right now (or R, for that matter),
> but doesn't it say that something like the following works?
> 
> fit.lm <- lm(y ~ x)
> fit.glm <- update(fit.lm, class = "glm")
> 
> But this isn't implemented in R, right? If one can make a wish, it would
> be really nice being able to (using weihong's example):
> 
> bar <- update(foo, . ~ . + (1|yr), class = "lmer")
> 
> 
> //Henric

It's not very convenient from the point of view of dispatch.  The
dispatch rules are such that the update method for the lm or glm class
would need to be aware of the lmer class to be able to do this.  The lm
and glm classes predate lmer by a long time.