R devel - Jun 2011 - Default values in control list of function

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

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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