[R] getting parts returned by lmer

David Winsemius dwinsemius at comcast.net
Mon May 3 16:16:32 CEST 2010

On May 3, 2010, at 9:41 AM, John Sorkin wrote:

> R 2.10.0
> windows XP
> I am trying to get the coefficients returned from lmer. Normally I  
> would use the names function to get the objects returned by the  
> function. This does not work in lmer, but it does for lm:

When you read the help page for lmer it refers your to the description  
of "mer"-class where that help page tells you that it is an S4 object  
and offers a wide variety of extractor method functions, including a  
coef function. The str function would have shown you the slot names,  
but at your level of knowledge, it would probably be safer to work  
with the extractor/accessor functions. (I speak from sad experience.  
The authors of that package know a lot more than either of us.)

> <- lmer(Reaction ~ Days + (1|Subject) + (0+Days|Subject), sleepstudy)
>> names(fm2)
>> fitlm <- lm(Reaction ~ Days, sleepstudy)
>> names(fitlm)
> [1] "coefficients"  "residuals"     "effects"       "rank"
> [5] "fitted.values" "assign"        "qr"            "df.residual"
> [9] "xlevels"       "call"          "terms"         "model"
> How does one know what is returned by lmer, and how does one access  
> the various parts? I looked at the code for lmer, but at least on my  
> level of R sophistication, the nature of the data returned in not  
> clear.
> Thanks,
> John
> John David Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
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David Winsemius, MD
West Hartford, CT

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