[Rd] help files for load and related functions

[Duncan Murdoch]

On 12/17/2007 9:06 AM, Oleg Sklyar wrote:
> Dear Patrick,
> 
> Firstly, and most importantly, I do not think that your post qualified
> for Rd! Please use the correct mail list for such things: R-help. I do
> not think anybody on Rd wants mailboxes clogged with irrelevant
> messages.

Since Patrick's message was about changes to the documentation, I think 
it is relevant to this list.

Duncan Murdoch

> Back to your question: it is not clear if you are confused, or your
> 'user' is confused, but all three help pages look pretty clear and
> straight forward to me. Moreover,  I do not see any connection between
> attach and library, which you find logical:
> 
> - load - the general use of this one is to load external data sets, e.g.
> load serialised R object(s) (as the example shows). Until you load, you
> cannot use the object as it has no relation to the R session and can be
> e.g. a file sitting somewhere on a network
> 
> - attach - the general use of this one would be to access elements of a
> data set directly, without the data set name specifier and the accessor
> operator, such as $, thus as the help page states - it is used to add
> the data set to the search path (as the example shows). If you look at
> the example, you do not have to call attach to be able to use data, data
> could have existed there before and what you effectively get with attach
> is a more convenient way of dealing with the data
> 
> - library - is used to load *and* attach an R package, which is not
> exactly the same as a serialised R object(s), but a full set of other
> functionality. Attaching packages is just a part of the loading process,
> which occurs basically when the package becomes visible to the user.
> Same as with load, you cannot use the package until you load it. There
> is not a hint of similarity between loading a package and attaching a
> data set as I see it. 
> 
> Regards,
> Oleg
> 
> On Mon, 2007-12-17 at 11:00 +0000, Patrick Burns wrote:
>> I recently had a discussion with a user about loading
>> and attaching in R.  I was surprised that the help files
>> don't  provide a very clear picture.
>> 
>>  From my point of view 'load' and 'attach' are very
>> similar operations, the difference being that 'attach'
>> creates a new database on the search list while 'load'
>> puts all the objects into the global environment.
>> 
>> The help file for 'load' is inexplicit that this is what
>> happens.  The 'load' and 'attach' help files neither refer
>> to the other in their See Also.
>> 
>> Furthermore, the 'library' help file talks about "loading"
>> packages.  I would suggest that it should use "attaching"
>> as that is the analogous operation.
>> 
>> None of these three help files (nor that of 'save') has a
>> Side Effects section.  Personally I think that all help files
>> should have a Side Effects section (to make it clear to
>> new users what side effects are and that they are not a
>> good thing for most functions to have).  I can understand
>> there could be another point of view on that.  However, I
>> definitely think that there should be a Side Effects section
>> in the help files of functions whose whole point is a side
>> effect.
>> 
>> Patrick Burns
>> patrick at burns-stat.com
>> +44 (0)20 8525 0696
>> http://www.burns-stat.com
>> (home of S Poetry and "A Guide for the Unwilling S User")
>> 
>> ______________________________________________
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