[Rd] A couple of issues with colClasses/setAs

Prof Brian Ripley ripley at stats.ox.ac.uk
Wed Sep 8 18:49:52 CEST 2004

On 8 Sep 2004, Peter Dalgaard wrote:

> Peter Dalgaard <p.dalgaard at biostat.ku.dk> writes:
> > To make it actually work, we should probably fixup the "what" that is
> > being passed to scan a bit further upstreams.
> > 
> > 
> > > Might be a good idea to teach colClasses about "factor".
> > 
> > That's what I thought. Other ideas would be to predefine some standard
> > date classes (it's a bit annoying that there's no way to give
> > auxiliary information like formats), and maybe to allow a second
> > header line containing class names.
> Done already, I see (except the class-header idea, which probably
> requires more thought). Thanks.

I've done some.  If you allow columns to be dropped it gets increasing 
hard to work out what as.is for example refers to, so I am looking at 
allowing named vectors.

> While we're in there should we perhaps consider adding pseudo-classes
> "Ymd"
> "dmY"
> "mdY"
> "Y/m/d"
> "d/m-Y"
> "m/d/Y"
> etc?  Or perhaps it is better with a catchall "Date-fmt", i.e., e.g.,
> "Date-%Y%m%d"? That'd be fairly easy to code:
> else if (length(grep("^Date-",colClasses[i])))  
>         as.Date(data[[i]], sub("^Date-(.*)$","\\1", colClasses[i]))
> although perhaps not so easy to document concisely.

Is it really so hard to convert such columns from character afterwards?

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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