From nashjc at uottawa.ca  Sun Jun 26 03:21:58 2011
From: nashjc at uottawa.ca (Prof. John C Nash)
Date: Sat, 25 Jun 2011 21:21:58 -0400
Subject: [Rd] Default values in control list of function
Message-ID: <4E0689B6.6090103@uottawa.ca>

In building a function for a package, I'd like to set the defaults in a control list,

e.g.,

makeg<-function(parameters, eps = 1.0e-7, control=list(showwork=TRUE, rubbish=1.0e+101)){

    etc.
}

This does not provide showwork or rubbish within the function if control() is not fully
specified. Copying others, I've previously set the control defaults within the function
then matched names, and that certainly works. I'm happy to keep using that approach, but
would like to have a pointer to good practice for doing this (I'm prepared to write or
help write a short tutorial if none exists).

I can understand that trying to do the default replacement at a second or greater level
could give problems. A search through the language definition and some googling didn't
show up any obvious warning about this, but I'm sure there are some comments somewhere.
Can anyone suggest some URLs?

One gets used to the nicety of being able to specify defaults and forgets that even R has
some limits.

JN



[Rd] Default values in control list of function
Prof. John C Nash