[R-sig-ME] extracting name of random slope from mer object

[Sven Hohenstein]

Hi Dan,

you can use the following approach to extract the names of  
random-slope variables:

# the model terms
term <- terms(model)
# all variables
vars <- as.character(attr(terms, "predvars")[-1])
# fixed variables
varsFix <- as.character(attr(terms, "predvars.fixed")[-1])
# random factors
varsRan <- names(ranef(model))

# Now, the names of the fixed variables and the random factors
# can be removed from the vector including all variable names:
Reduce(setdiff, list(vars, varsFix, varsRan))


This approach works with lme4 version 0.99999911-7. It might not work  
with models created with earlier versions of lme4.

Best,
Sven





Quoting Daniel Ezra Johnson <danielezrajohnson at gmail.com>:

> Hello,
>
> I can extract the name(s) of random intercept variable(s) with this command:
>
>> names(VarCorr(model))
>
> Is there any easy way to extract the names of random slope variables?
> I can't find it anywhere in str(model).
>
> Thanks a lot,
> Dan
>
> P.S. I know I could compare the list of all variables, e.g.
>
>> names(model.frame(model))
>
> with the headings inside e.g. ranef(model), and match it up that way, but I
> was wondering if there was anything easier.
>
> Also, I can't use model at call because I'm calling lmer() out of another
> function!
>
> 	[[alternative HTML version deleted]]
>
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>

-- 
Sven Hohenstein
Department of Psychology
University of Potsdam
Karl-Liebknecht-Str. 24-25
14476 Potsdam
Germany
Tel.: ++49 331-977 2370