[R] customizing help()

[Prof Brian D Ripley]

On Tue, 4 Apr 2000, Prof Brian D Ripley wrote:

> On Tue, 4 Apr 2000, Kurt Gerber wrote:
> 
> > Hi
> > I tried to customize help(), so it starts the compiled html help, and
> > searches in all packages.
> > 
> > I wrote the following function:
> > 
> >  > my.help
> > function(topic){
> > help(topic, package=.packages(all=T), lib.loc=.lib.loc, chmhelp=T)
> > }
> > 
> > When I use it with
> > 
> > >my.help(help)
> > 
> > give the following error:
> > 
> > Error in help(topic, package = .packages(all = T), lib.loc = .lib.loc,  :
> >         No documentation for `topic'
> > 
> > I tried also with
> > > my.help
> > function(x){
> > help(x,chmhelp)}
> > 
> > with the same result.
> > Only doing help(help) is working. Why my function doesn't work?
> 
> Because the first argument of help() is handled specially, to allow
> help(help) or help("help").  my.help(help) passes the help object to help,
> not "help".  But my.help("help") will still fail.
> 
> I could tell you how to do this, but I do think it is a bad idea, and
> we worked quite hard to do something better in 1.0.0.  The problem is that
> those options will find a copy of the help under a given name, and quite
> possibly not help for the object in the packages you have loaded.

Perhaps that was a bit mean, and the general principle at least may be
illuminating.  The following should work:

my.help <- function(...)
{
    oc <- match.call()
    oc[[1]] <- as.name("help")
    oc$package <- quote(.packages(all = T))
    oc$lib.loc <- quote(.lib.loc)
    oc$chmhelp <- TRUE
    eval.parent(oc)
}

Martin Maechler mentioned help.search(), which is very useful but does not
pick up the help file(s) directly.

-- 
Brian D. Ripley,                  ripley at 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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