[R] help in R 2.9.x for R 2.10.x packages

[Duncan Murdoch]

On 29/01/2010 2:34 PM, Michael Friendly wrote:
> [Env: Win Xp]
> Is there any options() setting or call to help()  or help.start() that 
> will allow me to view a help file for
> a package built under R 2.10.x under R 2.9.2?
>
> I'm using both R 2.9.2 and R 2.10.1, but prefer the former because the 
> CHM help is so much easier
> to use. Yet, if I install a package built for R 2.10.x, I can't find 
> *any* way to display a help file in this
> package.
>
> For example, after library(TeachinDemos),
>  > ?HWidentify
> Error in print.help_files_with_topic(x) :
>   No text help for 'HWidentify' is available:
> corresponding file is missing
> In addition: Warning message:
> In 
> print.help_files_with_topic("C:/R/R-2.9.2/library/TeachingDemos/chm/HWidentify") 
> :
>   No CHM help for 'HWidentify' in package 'TeachingDemos' is available:
> the CHM file for the package is missing
>
> So, I try
>  > help.start()
> updating HTML package listing
> updating HTML search index
> If nothing happens, you should open 'C:\R\R-2.9.2\doc\html\index.html' 
> yourself
>
> I can then get to
> file:///C:/R/R-2.9.2/library/TeachingDemos/html/00Index.html
> but then all the links there give Not Found, e.g.,
> file:///C:/R/R-2.9.2/library/TeachingDemos/html/HWidentify.html
>
> and, indeed, C:\R\R-2.9.2\library\TeachingDemos\html contains
> only 00Index.html.
> All the links therein are to .html files in the same directory, so of course
> are wrong.
>   
The CHM help files were built at package install time.  Binary packages 
are images of already-installed packages, so they won't have CHM files 
unless installed in 2.9.x or earlier.

So you "just" need to get the package source, and install it into the 
earlier R.  Sometimes this is easy, sometimes not.

Duncan Murdoch