[R-sig-ME] R: Re: GLMM family=binomial, link identity

[Ben Bolker]

On 13-02-26 05:57 PM, maggenga at libero.it wrote:
> Sorry, i was wrong. I want say lme4 package.
> 
> 
> But "glmer(...,family=binomial(link="identity")) " give me same results
> 
> as
> 
> "glmer(...,family=binomial(link="logit")) "
> 
> Why?
> 
> I want interpret the coefficients as risk difference and not OR
> 
> Thank you very much
> 
> Davide

[cc'ing back to r-sig-mixed-models: it's best to keep these
conversations on-list]

  It's hard to say without a reproducible example
<http://tinyurl.com/reproducible-000>.  I made up an example that seemed
to work, sort of -- at least it showed that I do *not* get the same
results.  With the stable version of lme4, the fit worked with the
default (logit) link and failed with the identity link (although
apparently for reasons of numerical instability, not because it's
impossible to fit such models).  With the development version (latest
version from github), both worked, and the identity link results seem to
have correctly estimated the parameters (I can tell because the data
were simulated).

See

http://rpubs.com/bbolker/4671

> 
> 
> 
>> ----Messaggio originale----
>> Da: bbolker at gmail.com
>> Data: 26/02/2013 23.40
>> A: <r-sig-mixed-models at r-project.org>
>> Ogg: Re: [R-sig-ME] GLMM family=binomial, link identity
>>
>> maggenga at ... <maggenga at ...> writes:
>>
>>>
>>> Hi,
>>> I'm phd student in medical statistics.
>>> I would like know the R-way to perform the identity link (family=binomial) 
> in
>> lmer (ade4 package).
>>
>>  How about
>>
>> glmer(...,family=binomial(link="identity")) 
>>
>> ?
>>
>> See ?family in base R.
>>
>> Warning: this is likely to be fragile (as fitting with non-standard
>> link functions often is).
>>
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>>
> 
>