[R-lang] Error message in mixed-effects logistic regression

[Andy Fugard]

> 
> tdMID.lmer1=lmer(Response~Bias+Day*Step+(1+Day*Step|Subject),data=E1tdMID,fa
> mily="binomial")
> 
> and the error message I get is as follows:
> 
> Error in if (any(sd < 0)) return("'sd' slot has negative entries") : 
>         missing value where TRUE/FALSE needed

If an sd (standard deviation) comes out negative then something has 
broken somewhere.  The random effect specification

   1+Day*Step|Subject

Asks for a random intercept for each subject, and a random slope per 
subject for: day, step, and the interaction of day and step --- the 
error is probably indicative of insufficient data to fit a model this 
complicated.

A

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