[R-sig-ME] Bleeding edge lme4 (or lme4a) plus DF estimation

[Ben Bolker]

Joehanes, Roby (NIH/NHLBI) [F] <roby.joehanes at ...> writes:

> I discovered a bug on your lme4Eigen's refit function. 
> This is on version 0.9996875-9 (Description
> revision 169). I hope I got this right. If the original data
>  matrix has some missing data in it, somehow the X
> and Z matrices (and y column) are correctly trimmed (i.e., the rows
>  with missing data are removed).
> However, if I fit it with another y column, it reports error due 
> to length mismatch. The error is as follows:
> Error: length(newresp <- as.numeric(as.vector(newresp))) == length(rr$y) 
> is not TRUE
> 
> Should I try the latest version and see if this bug has been fixed?

  It probably hasn't.  It would be very helpful if you could send a small
self-contained example to lme4-authors <at> r-forge.wu-wien.ac.at --
we could probably make one up ourselves, but it would be quicker/
more motivational if you did it.

> 
> Also, will update method speed up computation
>  if I changed the X (or Z) matrix a little bit by swapping or
> adding up to three columns (from about 40+ columns)? 

  Probably not -- refit saves time by (1) starting from previous
starting values and (2) not having to rebuild X and Z components.
You could do #1 yourself by doing something like setting

update(...,start=getME(prevfit,"theta"),...)

(I think).