[R] URL error when trying to use help function in R [Sec: UNOFFICIAL]

[Peter Dalgaard]

On 09/10/2010 01:03 AM, David Winsemius wrote:
> 
> On Sep 9, 2010, at 6:34 PM, Gosse, Michelle wrote:
> 
>> Greetings,
>>
>> I am using R version 2.11.1 on a Dell computer, via a VMware  
>> connection to a remote server. My browser version is IE  
>> 8.0.6001.18702 and the OS is some corporate version of Microsoft XP.
>>
>> I'm trying to learn more about the tapply function , so I typed ? 
>> tapply into the command line. This opened up a browser window with  
>> url http://127.0.0.1:28138/library/base/html/tapply.html which is  
>> giving me an error message.
>> I receive the same problem when trying for help on other commands,  
>> e.g. ?table http://127.0.0.1:28138/library/base/html/table.html and ? 
>> log http://127.0.0.1:28138/library/base/html/Log.html
>>
>> I did a whois on 127.0.0.1
> 
> That should always be your own computer. The browser is trying to  
> reach a server on itself over port 28138 and either the port is  
> blocked or you don't have the documentation at that location.

The _real_ problem is likely that the server is really running on the
remote computer. Substituting the remote server name for 127.0.0.1 is
not unlikely to make things work. (Notwithstanding firewalls and the like).

It is a generic weakness of our current dynamic HTML setup, or of
current browser technology if you like. Same thing with file:// URLs --
if you try to view them in a browser and you already have a browser on
your display, but running on a different machine than the one with the
file, you get a "file not found". So when R on machine B wants to
display a help page, it sends a message to the browser to connect to R's
own server on B  by specifying a port on localhost (127.0.0.1), but if
this request gets forwarded to a browser on machine A, then it goes
looking for a server on _its_ localhost, i.e. machine A, and it isn't
there...

I suppose we could do somewhat better, but I don't feel too confident
about the various platform issues. As far as I can see, we currently
hardcode "http://127.0.0.1" inside the help print method in
utils:::print.help_file_with_topics(), and I suspect we could make that
a user option, or try to be more intelligent about finding the machine's
own IP address.

A pragmatic way out is always options(help_type="text").


-- 
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com