From ggrothendieck at gmail.com  Sun Jun 26 04:38:35 2011
From: ggrothendieck at gmail.com (Gabor Grothendieck)
Date: Sat, 25 Jun 2011 22:38:35 -0400
Subject: [Rd] Default values in control list of function
In-Reply-To: <4E0689B6.6090103@uottawa.ca>
References: <4E0689B6.6090103@uottawa.ca>
Message-ID: <BANLkTimsuvKOOaV+Btzbqp8QuhSHcxe7JA@mail.gmail.com>

On Sat, Jun 25, 2011 at 9:21 PM, Prof. John C Nash <nashjc at uottawa.ca> wrote:
> 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.
>

See ?modifyList



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[Rd] Default values in control list of function
Gabor Grothendieck