[Rd] error in install.packages() (PR#14042)

[Prof Brian Ripley]

I agree it is a good idea, but a new name seems justified to avoid 
confusion.

On Wed, 4 Nov 2009, Duncan Murdoch wrote:

> On 11/4/2009 12:15 PM, William Dunlap wrote:
>>> -----Original Message-----
>>> From: r-devel-bounces at r-project.org [mailto:r-devel-bounces at r-project.org] 
>>> On Behalf Of Duncan Murdoch
>>> Sent: Wednesday, November 04, 2009 8:47 AM
>>> To: michael.m.spiegel at gmail.com
>>> Cc: R-bugs at r-project.org; r-devel at stat.math.ethz.ch
>>> Subject: Re: [Rd] error in install.packages() (PR#14042)
>>> 
>>> On 11/4/2009 11:05 AM, michael.m.spiegel at gmail.com wrote:
>>> > Full_Name: Michael Spiegel
>>> > Version: 2.10
>>> > OS: Windows Vista
>>> > Submission from: (NULL) (76.104.24.156)
>>> > > > The following error is produced when attempting to call 
>>> install.packages.  Here
>>> > is the results of the traceback:
>>> > >> source('http://openmx.psyc.virginia.edu/getOpenMx.R')
>>> > Error in f(res) : invalid subscript type 'list'
>>> >> traceback()
>>> > 7: f(res)
>>> > 6: available.packages(contriburl = contriburl, method = method)
>>> > 5: .install.winbinary(pkgs = pkgs, lib = lib, contriburl = contriburl, > 
>>> method = method, available = available, destdir = destdir, > 
>>> dependencies = dependencies, ...)
>>> > 4: install.packages(pkgs = c("OpenMx"), repos = repos)
>>> > 3: eval.with.vis(expr, envir, enclos)
>>> > 2: eval.with.vis(ei, envir)
>>> > 1: source("http://openmx.psyc.virginia.edu/getOpenMx.R")
>>> > > I've tracked the error down to somewhere in available.packages defined 
>>> in
>>> > src\library\utils\R\packages.R.  I am guessing that the error in version 
>>> 2.10
>>> > has something to do with the change: "available.packages() gains a 
>>> 'filters'
>>> > argument for specifying the filtering operations performed on the 
>>> packages found
>>> > in the repositories."
>>> 
>>> I've found the error, and will fix and commit to R-devel and R-patched.
>>> 
>>> For future reference:  the problem was that it assigned the result of 
>>> sapply() to a subset of a vector.  Normally sapply() simplifies its result 
>>> to a vector, but in this case the result was empty, so sapply() returned 
>>> an empty list; assigning a list to a vector coerced the vector to a list, 
>>> and then the "invalid subscript type 'list'" came soon after.
>> 
>> I've run into this sort of problem a lot (0-long input to sapply
>> causes it to return list()).  A related problem is that when sapply's
>> FUN doesn't always return the type of value you expect for some
>> corner case then sapply won't do the expected simplication.  If
>> sapply had an argument that gave the expected form of FUN's output
>> then sapply could (a) die if some call to FUN didn't return something
>> of that form and (b) return a 0-long object of the correct form
>> if sapply's X has length zero so FUN is never called.  E.g.,
>>    sapply(2:0, function(i)(11:20)[i], FUN.VALUE=integer(1)) # die on
>> third iteration
>>    sapply(integer(0), function(i)i>0, FUN.VALUE=logical(1)) # return
>> logical(0)
>> 
>> Another benefit of sapply knowing the type of FUN's return value is
>> that it wouldn't have to waste space creating a list of FUN's return
>> values but could stuff them directly into the final output structure.
>> A list of n scalar doubles is 4.5 times bigger than double(n) and the
>> factor is 9.0 for integers and logicals.
>
> That sounds like a good idea.  It would be a bit of work, because the current 
> sapply depends on lapply while this would need its own internal 
> implementation:  but it would probably be worthwhile.
>
> Duncan Murdoch
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595