Message-ID: <5D526ED7-71B6-4DC7-9DC4-B92C97CE307A@virginia.edu>
Date: 2008-03-30T17:48:01Z
From: Michael Kubovy
Subject: Clash between alr3 and AlgDesign. (Was: Re: Second & subsequent calls to function fails. Please help debug.)
In-Reply-To: <47EFCF8F.6070700@stats.uwo.ca>
Hi Duncan,
Yes, I came to realize that ifelse was not the way to go. Here is how
I dealt with it:
if(sum('AlgDesign' == (.packages())) > 0) detach('package:AlgDesign')
It requires me (and my students) to learn only the (.packages())
construct (and avoid knowing anything about search(), match() or pos).
As a former student of mine (who has long since gone into business)
once said: "I avoid learning experiences like the plague."
Thanks again,
Michael
On Mar 30, 2008, at 1:36 PM, Duncan Murdoch wrote:
> On 30/03/2008 10:06 AM, Michael Kubovy wrote:
>> I've been trying to dynamically detach and attach things in my
>> Sweave, in order to circumvent the problem.
>> Here is my first attempt:
>> pkg <- 'package:AlgDesign'
>> p <- is.na(match(pkg, search()))
>> ifelse(p == FALSE, detach(pkg), NA)
>
> You can't use detach this way. It is fine to say
> detach("package:AlgDesign") or detach(AlgDesign), but the way detach
> is written, you're attempting to detach something named "pkg".
>
> This rewrite of your code is untested, but I think it should work:
>
> pkg <- 'package:AlgDesign'
> p <- match(pkg, search())
> if (!is.na(p)) detach(pos=p)
> require(alr3)
>
> I've also changed your ifelse() to if (), and not just because I
> don't need an else clause: ifelse() is designed to do computations
> on vectors, if() is designed for flow control. I think we want flow
> control here.
>
> Duncan Murdoch
_____________________________
Professor Michael Kubovy
University of Virginia
Department of Psychology
USPS: P.O.Box 400400 Charlottesville, VA 22904-4400
Parcels: Room 102 Gilmer Hall
McCormick Road Charlottesville, VA 22903
Office: B011 +1-434-982-4729
Lab: B019 +1-434-982-4751
Fax: +1-434-982-4766
WWW: http://www.people.virginia.edu/~mk9y/