[Lign251] BLUPs

[Roger Levy]

Leslie Lee wrote:
> Hi,
> 
> For 7.1(ii), I tried to generate the BLUPs:
> 
>> b2=ranef(aa.f1.lmer)
> 
> Even though this gives me 2 (unnamed) columns of 76 rows, corresponding to
> the speaker and the BLUPs, R doesn't seem to treat this as a regular data
> frame:
> 
>> summary(b2)
>         Length Class      Mode
> Speaker 1      data.frame list
> 
> The length of the thing is only 1, even though I see 2 columns and 76
> rows. I also can't access either column in the thing. How do I change this
> into a regular dataframe or into a vector?

Hi Leslie,

Good question: what's going on is that ranef() returns a list.  For
information on lists, read chapter 6 of:

  http://cran.r-project.org/doc/manuals/R-intro.pdf

Each component of the list corresponds to one of the clusterings of the
data -- so for example, applying ranef() to a model like

  lmer(rt ~ Freq + (1 | Subj) + (1 | Item))

would give you a two-component list: a Subj component and an Item
component.  Each component is itself a data frame where each column is a
cluster-level parameter and each row is a cluster.  What you want to do is

  b2 <- ranef(aa.f1.lmer)[[1]]

or

  b2 <- ranef(aa.f1.lmer)$Speaker

or

  b2 <- ranef(aa.f1.lmer)[["Speaker"]]

Hope this helps!

Roger


-- 

Roger Levy                      Email: rlevy at ling.ucsd.edu
Assistant Professor             Phone: 858-534-7219
Department of Linguistics       Fax:   858-534-4789
UC San Diego                    Web:   http://ling.ucsd.edu/~rlevy