R devel - May 2006 - Changing the generic of as.data.frame

I have changed the generic to as.data.frame in R-devel by adding a '...'
argument.  This means that any methods which do not have a '...'
argument
(quite a few do) will generate a warning in R CMD check: the fix is very 
simple (and backwards compatible): just add a '...' argument to the 
method.

We already had a problem with as.data.frame.table which had an extra 
argument (at the request of users), but required that the method had to be 
called explicitly to use.  Adding as.data.frame.ftable compounded that 
problem.

Packages that have S4 methods for as.data.frame still work *unless* they 
set an explicit generic (as FLCore does).

The other motivation was to allow the option to not convert character 
vectors to factors, which needed an additional argument to 
as.data.frame.character.  So data.frame now has an argument
'charToFactor'
controlled by a global option (which also controls the default of as.is in 
read.table).  More experience will be needed as to whether it is safe to 
work with the global option set to FALSE, so that aspect should be 
regarded as experimental until 2.4.0 is released or it is withdrawn.

-- 
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

On Mon, 22 May 2006, Prof Brian Ripley wrote:
> The other motivation was to allow the option to not convert character
> vectors to factors, which needed an additional argument to
> as.data.frame.character.  So data.frame now has an argument
'charToFactor'
> controlled by a global option (which also controls the default of as.is in
> read.table).  More experience will be needed as to whether it is safe to
> work with the global option set to FALSE, so that aspect should be
> regarded as experimental until 2.4.0 is released or it is withdrawn.
Splus's data.frame() and as.data.frame() have had the
'stringsAsFactors'
argument to data.frame and as.data.frame since version 6.0 (2001).  Their
default values come from options("stringsAsFactors").  read.table()
and
a few other data.frame-oriented functions have the same argument.
It looks like stringsAsFactors has the same functionality as your
new charToFactor.  Would it be feasible to change its name to stringsAsFactors?

Splus> help(data.frame)
                     Construct a Data Frame Object

USAGE:

data.frame(..., row.names, check.rows=F, check.names=T,
           na.strings="NA", dup.row.names=F,
stringsAsFactors=<<see below>>)
data.frameAux(x, ...)
as.data.frame(x, row.names=NULL,  stringsAsFactors=<<see below>>,
...)
is.data.frame(x)
...
   stringsAsFactors
          a logical flag; if TRUE then convert character arguments
          to factors whose levels are the unique strings in the
          argument. This may save time and space if there a many
          repeated values in the strings and may make the
          statistical modelling functions easier to use. The
          default is TRUE, unless one sets options(stringsAsFactors=FALSE).
...


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