[FORGED] Re: Question about gls

G'day Rolf,

On Sat, 24 Mar 2018 10:52:34 +1300

On 24/03/18 08:58, Andrzej Galecki wrote:

Hi Louise,

One possible way ...

[...]

Not exactly obvious, but, is it?  How on earth would one ever figure 
this out, except by appealing to r-sig-mixed-models?

Well, in the good old days, over on r-help, whenever people complained
that it was not obvious how to do something using the MASS package they
were gently but firmly reminded by a certain person that the MASS
package is support software for a certain book and that they should
read the fine book (RTFB). :)

I believe Doug Bates is far to polite to point out the the nlme package
is also support software for a certain book and that you need to RTFB
for the gory details.....

Looking at str(fit.gls) one sees that there is a (list) component 
"modelStruct" and that this component in turn has a component 
"corStruct".  If one is an optimist, one might try

     fit.gls$modelStruct$corStruct

which (mirabile dictu!) gives:

[...]

Again if one is an optimist, one might try stripping away all the 
unwanted baggage by doing

     as.vector(fit.gls$modelStruct$corStruct)

[...]

Still it's all pretty obscure.  And typical of the obfuscation that 
results from using S4 classes and methods.

I see that Doug has corrected you already, but the fact that you are
typing `$` all the time instead of `@` should have been a dead give
away that this is S3, not S4.  Of course, the length of time that the
nlme package is around is another give away....

Cheers,

	Berwin