[R] Introduce a new function in a package?

[Don MacQueen]

Expressions in .Rprofile are executed *before* any previously saved 
global environment is loaded (i.e., before the .RData file in the 
current working directory is loaded, causing the message " 
[Previously saved workspace restored]" to a appear).

If you define a function in .Rprofile, and then later answer "yes" to 
the "Save workspace image?" question when you quit R, the function 
will exist in the saved workspace.

When you next start R, the version that comes in from .Rprofile will 
be replaced by the version in the saved workspace -- because the 
saved workspace is loaded after .Rprofile is executed.

This means that if you decide to change the function in .Rprofile, 
your changes will immediately be lost when the previously saved 
workspace is loaded, since that has the previous version.

So defining personal utility functions in .Rprofile is not very 
effective. Much, much, better to create a package, and then require() 
that package in .Rprofile. And since creating a package is really 
very easy, I strongly recommend that option.

Saving the functions in an image file and then attaching it is fine, 
but less convenient, in my opinion, since you have to keep track of 
where it is in the file system.

-Don

At 4:09 PM +0100 4/6/05, Jan T. Kim wrote:
>On Wed, Apr 06, 2005 at 09:57:00AM -0400, Roger D. Peng wrote:
>>  I think the usual way is to create an R package for yourself and load
>>  it when you need it for whatever project.
>>
>>  -roger
>
>Alternatively, one can also write the function in question into one's
>~/.Rprofile; then, it's automatically available in all R sessions.
>To avoid confusion, make sure that you choose a unique name, i.e. one
>that isn't used by any package, if possible.
>
>This method should be used only for functions intended to provide some
>convenience in interactive sessions, code in scripts should not rely
>on functions being provided by ~/.Rprofile. For scripting, an R package
>is definitely preferred.
>
>Best regards, Jan
>
>>  Luis Ridao Cruz wrote:
>>  >R-help,
>>  >
>>  >Sometimes I define functions I wish to have in any R session.
>>  >The obvious thing to do is copy-paste the code
>>  >The thing is that sometimes I don't know where I have the function
>>  >code.
>>  >
>>  >My question is if somehow I could define a function and "introduce" it
>>  >(let's say 'base' package ) so that
>>  >could be used anytime I run a different R project.
>>  >
>>  >Thank you in advance
>>  >
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>--
>  +- Jan T. Kim -------------------------------------------------------+
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-- 
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA