[R-sig-ME] lme4 merMod model object

[Fox, John]

Dear Nathan,

I'm glad that you were able to solve your problem.

The documentation in help files is relatively brief and can be cryptic, but there are also many examples in ?linearHypothesis that illustrate how to specify hypotheses. 

Best,
 John

> -----Original Message-----
> From: Nathan Pace [mailto:n.l.pace at utah.edu]
> Sent: Monday, November 20, 2017 12:06 AM
> To: Fox, John <jfox at mcmaster.ca>
> Cc: R-sig-mixed-models <r-sig-mixed-models at r-project.org>
> Subject: Re: lme4 merMod model object
> 
> Hi John,
> 
> Your example was just what I needed.
> 
> I can see now that your example is an illustration of this sentence in the
> documentation:
> 
> “Alternatively, the hypothesis can be specified symbolically as a character
> vector with one or more elements, each of which gives either a linear
> combination of coefficients, or a linear equation in the coefficients (i.e., with
> both a left and right side separated by an equals sign).”
> 
> I must confess to an inability at times to translate words in documentation into
> code.
> 
> So, you sample code was very helpful.
> 
> 
> Nathan
> 
> On 1811//2017, 7:45 AM, "Fox, John" <jfox at mcmaster.ca> wrote:
> 
>     Dear Nathan,
> 
>     Yes, you should be able to use linearHypothesis() in the car package. The
> command would be something like
> 
>     linearHypothesis(your.model, c("coef1 - coef2 = 0",  "coef3 - coef4 = 0"))
> 
>     You could equivalently specify the hypothesis as c("coef1 - coef2",  "coef3 -
> coef4"), with the 0s implied, or as c("coef1 = coef2",  "coef3 = coef4 ").
> 
>     I'm curious why that wasn't clear from ?linearHypothesis.
> 
>     I hope this helps,
>      John
> 
>     -----------------------------
>     John Fox, Professor Emeritus
>     McMaster University
>     Hamilton, Ontario, Canada
>     Web: socialsciences.mcmaster.ca/jfox/
> 
> 
> 
>     > -----Original Message-----
>     > From: R-sig-mixed-models [mailto:r-sig-mixed-models-bounces at r-
> project.org]
>     > On Behalf Of Nathan Pace
>     > Sent: Friday, November 17, 2017 7:02 PM
>     > To: R-sig-mixed-models <r-sig-mixed-models at r-project.org>
>     > Subject: [R-sig-ME] lme4 merMod model object
>     >
>     > Hi mixed model experts,
>     >
>     > I have a GLMM (binomial) model estimated in lme4 using glmer.
>     >
>     > There are many linear coefficients such as coef1, coef2, coef3, coef4, …
>     >
>     > I have used glht from multcomp to test coefficient contrasts such as coef1 –
>     > coef2 = 0.
>     >
>     > Now I desire to test sets of linear contrasts in the model jointly such as
> coef1 –
>     > coef2 = 0 & coef3 – coef4 = 0.
>     >
>     > By my reading, this should be possible in the linearHypothesis function of
> the
>     > car package.
>     >
>     > If someone has already used sets of contrast vectors for that purpose, I
> would
>     > appreciate learning of the format.
>     >
>     > Thanks,
>     >
>     > vd
>     > Nathan Pace
>     > University of Utah
>     >
>     >
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