[Rd] bug in options() - help page (PR#1323)

[o.christensen@lancaster.ac.uk]

Not all options listed on the help page for options() are set initially.
This should be said on the help page.

ripley@stats.ox.ac.uk wrote:
> 
> Much of this is not a bug.  The situation is complex.
> 
> The options list is dynamic: users can add new options at any time.
> Options need not be set, and which options are set depends on
> the platform.  Many options if unset have an internal default: this is a
> protection against a damaged set of options, in particular a broken system
> Rprofile file.
> 
> It is an incorrect assumption that setting the previous options returned
> does re-set the options: it only resets those that were previously set,
> not those set since.
> 
> In many cases setting an option to NULL will unset it.
> 
> There is at least one bug: download.info should not be set, it having been
> changed to internet.info (which has an internal default).
> 
> On Sat, 23 Feb 2002 o.christensen@lancaster.ac.uk wrote:
> 
> > Dear R-developers
> >
> > There is a discrepancy between the variables found by typing
> > names(options()) and the variables described on the help page for the
> > function ``options''.
> >
> > The following variables are in names(options()) but not described on the
> > help page :
> >
> > "error.messages"
> > "repositories"
> > "show.coef.Pvalues"
> > "help.try.all.packages"
> > "download.info"
> > "dvipscmd"
> 
> Some options are documented where they are used: numbers 2 and 4 are, I
> know.  I believe `error.messages' is obselete.
> 
> > Since options() is part of ``base R'' and the homepage claims that the
> > options described there are the only options used by ``base R'', this
> > may be considered as a
> > bug.
> 
> That claim is a bug, not least because ``base R'' is undefined!
> 
> > The following variables are described on the help
> > page, but are not in names(options()):
> >
> > error
> > show.error.messages
> > download.file.method
> > de.cellwidth
> > internet.info
> 
> Right. They can be set if needed, but have internal defaults.
> 
> > I had a problem with the option ``show.error.messages'' which may be
> > related to this option not being in names(options()) (I do not claim to
> > understand how options() really work).
> > Reporting and checking a problem with ``show.error.messages'' is
> > actually confusing, since this option changes the printed output from
> > errors. Here is the problem and my comments on the output (consider
> > starting a fresh R session).
> >
> > stop("test - err. mess. printed ")
> > ## prints error mesage, unless ``show.error.messages=FALSE''
> > op <- options()
> > options(show.error.messages=FALSE)
> > stop("test - err. mess. printed ")
> > ## as expected, nothing is printed
> > options(op)
> > stop("test - err. mess. printed ")
> > ## Reseting the options, we expect to see the print. Nothing is printed
> 
> That does not `reset the options', nor is that what the help page example
> says it does (note the word `initial').  The same thing happens with
> options("error").
> 
> I'll add an explicit default for that one.
> 
> --
> Brian D. Ripley,                  ripley@stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272860 (secr)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> 
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-- 
Ole F. Christensen
Department of Mathematics and Statistics
Fylde College, Lancaster University 
Lancaster, LA1 4YF, England

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