R devel - Feb 2010 - Package options

Dear all,

I am developing a package foo that has a namespace. I would like to be able to
provide an option, say opt, that

1) is set to a default value when the package is loaded
2) can be set to a different value by the package user
3) is used by functions within the package

How can I achieve this?

Cheers,
 
Chris Brien
Adjunct Senior Lecturer in Statistics
-----
School of Mathematics & Statistics - Mawson Lakes
Phenomics and Bioinformatics Research Centre
University of South Australia
GPO Box 2471
ADELAIDE? 5001? South Australia
Phone:? +61 8 8302 5873 ? Fax:? +61 8 8302 5785
Email:?? Chris.Brien at unisa.edu.au 
WEB page:? <http://people.unisa.edu.au/Chris.Brien> 
CRICOS No 00121B

On 03/02/2010 8:07 AM, Chris Brien wrote:
> Dear all,
> 
> I am developing a package foo that has a namespace. I would like to be able
to provide an option, say opt, that
> 
> 1) is set to a default value when the package is loaded
> 2) can be set to a different value by the package user
> 3) is used by functions within the package
> 
> How can I achieve this?
> 
Do you want this option to persist to the next session if a user saves 
the workspace?  If so, then it should be stored in a variable in the 
global environment.  You can use assign(".FooOptions", value, 
envir=globalenv()) to set it, and get(".FooOptions",
envir=globalenv())
to read it.

The obvious problem with this is that the user might already have a 
.FooOptions variable defined, and your code would stomp on it.  An 
alternative is to store the variable into the namespace.  You need to 
unlock it to change it.  See tools:::startDynamicHelp for code that does 
this for the variable httpdPort.

Duncan Murdoch