[seul-sci] Re: Followup: R-Taskhelps docs

["Pete St. Onge" <pete@seul.org>]

Hi Martin,

Thanks again for your feedback on the taskhelps document. I've modified it
today, and I wanted to follow up with you.

> A few things:
> 1) R-notes is now very outdated.
>    It's successor comes as part of R itself (from today's 0.99 release on)
          I installed 0.99 the day you emailed me; I did have a problem in
that the help files did not update (at least, not that I saw). I will be
completely removing my current version of R when 1.0 comes out at the end of
the month.

> 2) A typo:  From str(.), your two datasets seem to have "93" observations
>    ("records"), but in the text you say "934"
          Good call. Fixed.

> 3) "Comparing Regression Lines in R"
> 
>    ends with a pretty bad error :
> 
>    You compare two models that are *NOT* nested.
>    The reason that anova gives almost no output, is *NOT* that these two
>    models are so close, but that it is *NOT* possible to compare
>    non-nested models in a strict sense.
>    ("Strict" meaning: Comparison with a proper test for non-equality of
>    the models.).
          Here you hit upon a gap in my understanding of statistics. Zar's
text doesn't explain this at all ("beyond the scope of this book") and none
of my graduate stats courses (in biology, mind you) have covered this in
much detail either - that said, I will read up more on this when I get the
chance. In the meanwhile, I have removed that particular subsection. I will
later replace it with examples showing how to use the glm() function to
compare regressions having different n.

> In all these cases ---including yours--- I think it should be required
> that the datasets used are either part of R already {via  data(...)},
> or are available on the web via the  read.table.url(.) function
> (see its online help for a few examples).
          Completely agreed. I will be exploring the data sets in R more
closely after I install R1.0 (I've also indicated in the draft that I want
to change all of my examples to use existing R datasets)

> I don't claim that I've read through everything carefully, but I think
> why don't you go ahead an "publish" your link on R-help or even R-announce
> once you've corrected the above problem.
          I will be posting it to R-help shortly, to get more feedback, and
invite other submissions.

          I really appreciated your suggestions, and I'm hopeful that this
will be the start of a useful addition to a very useful stats package.

          Thanks!

          Pete

-- 
Pete St. Onge
pete@seul.org