Class "coef.mer" into a data.frame?

On Dec 31, 2010, at 2:49 AM, Jukka Koskela wrote:

Hello,

Could somebody please tell me what am I doing wrong in following?

I try extract coefficients (using arm-package) from the lmer  
frunction, but I get the
following warning:
a<-data.frame(coef(res))
Error in as.data.frame.default(x[[i]], optional = TRUE,  
stringsAsFactors = stringsAsFactors) :
cannot coerce class "coef.mer" into a data.fram

I think I have done it before the same way and it has worked, but  
not any more..

Are you sure you were not looking at just one particular element of  
a coef.mer object?

fm1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy)

a<-data.frame(coef(fm1))

Error in as.data.frame.default(x[[i]], optional = TRUE,  
stringsAsFactors = stringsAsFactors) :
  cannot coerce class '"coef.mer"' into a data.frame

coef(fm1)

$Subject
    (Intercept)       Days
308    253.6623 19.6665383
309    211.0067  1.8461362
310    212.4446  5.0170766
330    275.0971  5.6535771
<snipped>
.
.

a<-data.frame(coef(fm1)[[1]])
a

    X.Intercept.       Days
308     253.6623 19.6665383
309     211.0067  1.8461362
310     212.4446  5.0170766
330     275.0971  5.6535771
331     273.6664  7.3980095
<snipped>

-- 

David Winsemius, MD
West Hartford, CT