[R-sig-ME] Mixed Models

Emmanuel Curis emmanuel.curis at parisdescartes.fr
Tue Feb 16 17:14:02 CET 2016

Hi Jessica,

It is very difficult to help about the error message without more
details without more details on your dataset, but basically it means
that you have redundant information in your 'fixed effects' variables
(counfounding variables).

For instance, you may have only male (so "sex" is useless, redundant
with 1), or "dodgy" may be 1 only for males and 0 only for femalees,
to the two variables are in fact the same...

More subtle, « mass » may be an affine function of « length » (like
mass = 3 * length + 4 for instance), here again making these two
variables redundant.

Including confounding variables as fixed effects seems otherwise a
good starting point, but here again without any details about their
meaning, it's impossible to say if you are right in the syntax and so

Best regards,

On Tue, Feb 16, 2016 at 03:45:22PM +0000, Jessica Witt wrote:
« Hi,
« I’m very new to mixed modelling so please forgive me for this! I am trying to see the repeatability of a behaviour for individuals e.g. the area travelled, but I’ve also got a number of variables that could confound this so am I right in including these as fixed factors? 
« Furthermore I’ve written the code but it’s not giving me anything and I’m pretty unsure what the error message means, if someone could explain to me any modifications I need in my R code to get the repeatability of area travelled that would be amazing!
« areamod<-lmer(Area~1+Sex+Temp+Mass+Length+Dodgy+Tank+Order+(1|ID), data=platy, na.action=na.exclude, REML=TRUE)
« fixed-effect model matrix is rank deficient so dropping 1 column / coefficient
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                                Emmanuel CURIS
                                emmanuel.curis at parisdescartes.fr

Page WWW: http://emmanuel.curis.online.fr/index.html

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