[Rd] Changing the generic of as.data.frame

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon May 22 18:08:06 CEST 2006

On Mon, 22 May 2006, Bill Dunlap wrote:

> 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 regarded as experimental until 2.4.0 is released or it is withdrawn.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?

It would, but then I think we would want to ensure it did precisely the 
same thing.  If there a description of what exactly 
options("stringsAsFactors") affects?  (?options suggests it is data.frame, 
read.table and importData, and nothing else).

> Splus> help(data.frame)
>                     Construct a Data Frame Object
> 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).
> ...
> ----------------------------------------------------------------------------
> Bill Dunlap
> Insightful Corporation
> bill at insightful dot com
> 360-428-8146
> "All statements in this message represent the opinions of the author and do
> not necessarily reflect Insightful Corporation policy or position."

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

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