From bates at stat.wisc.edu  Thu May 15 17:28:59 2003
From: bates at stat.wisc.edu (Douglas Bates)
Date: Thu May 15 18:29:02 2003
Subject: [Rd] update.lme trouble (PR#2985)
In-Reply-To: <200305121554.h4CFsf2b019255@pubhealth.ku.dk>
References: <200305121554.h4CFsf2b019255@pubhealth.ku.dk>
Message-ID: <6ry918i37i.fsf@bates4.stat.wisc.edu>

p.dalgaard@biostat.ku.dk writes:

> Try this
> 
> data(Assay)
> as1 <- lme(logDens~sample*dilut, data=Assay,
>            random=pdBlocked(list(
>                      pdIdent(~1),
>                      pdIdent(~sample-1),
>                      pdIdent(~dilut-1))))
> 
> update(as1,random=pdCompSymm(~sample-1))
> update(as1,random=pdCompSymm(~sample-1))
> update(as1,random=pdCompSymm(~sample-1))
> update(as1,random=pdCompSymm(~sample-1))
> 
> I'm getting different results on different invocations!

I'm not sure exactly what the problem was but it could be triggered by
calling lme directly rather than through update.  That is, successive
calls to
  lme(logDens~sample*dilut, data=Assay, random=pdCompSymm(~sample-1))
would alternate between a successful fit and an error.

The problem does *not* occur with the current r-patched, which will be
released as R-1.7.1 in early June.  At least it does not occur under
Linux.  I would appreciate it if someone could check with r-patched
under Windows.

I have added this example as one of the tests in nlme_3.1-40, which
will be released before R-1.7.1


[Rd] update.lme trouble (PR#2985)
Douglas Bates