[R] Attributes or list programming "efficiency"

[Bert Gunter]

Thankyou Brian (and others). Very useful information(as usual).


-- Bert

-----Original Message-----
From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk] 
Sent: Wednesday, May 14, 2008 10:29 PM
To: Bert Gunter
Cc: r-help at r-project.org
Subject: Re: [R] Attributes or list programming "efficiency"

On Wed, 14 May 2008, Bert Gunter wrote:

> R-Fellow Travellers:
>
> Asked from the perspective of a software development amateur ...
>
> Suppose one wishes to create data structures that have both data and
> metadata -- e.g. a data.frame and details about where, when, and by whom
the
> data were gathered (specifics not important here).
>
> 1. Is there any inherent processing advantage in R in representing this as
a
> list that contains both the data and metadata as components vs as a
> data.frame with the metadata as attributes?
>
> 2. Is there a compelling software architecture argument to favor one vs
the
> other?
>
> I suspect the answer is no in both cases, but I thought I'd ask. This
seems
> to be mainly relevant for S3 programming, as in S4 one might stick the
info
> into different slots (if one wishes to dispatch on them).

The architecture is not designed for large numbers of attributes (and that 
includes slots in the current implementation) since they are stored as 
pairlists -- easy to grow, slow to search.  So if you have many (thousands 
or more) items of metadata, store them in a single character vector rather 
than as separate attributes.

Otherwise what is convenient for your way of working should win out.

>
> Cheers to all,
>
> Bert Gunter
> Genentech
>
>
>
>
>
>
>
>
> 	[[alternative HTML version deleted]]
>
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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