-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Prof
Brian Ripley
Sent: Sunday, December 26, 2004 2:04 AM
To: [EMAIL PROTECTED]
Subject: [Rd] R's IO speed
R-devel now has some improved versions of read.table and write.table.
For a million-row data frame containing one number, one
factor with few levels and one logical column, a 56Mb object.
generating it takes 4.5 secs.
calling summary() on it takes 2.2 secs.
writing it takes 8 secs and an additional 10Mb.
saving it in .rda format takes 4 secs.
reading it naively takes 28 secs and an additional 240Mb
reading it carefully (using nrows, colClasses and
comment.char) takes 16 secs and an additional 150Mb (56Mb of
which is for the object read in).
(The overhead of read.table over scan was about 2 secs,
mainly in the conversion back to a factor.)
loading from .rda format takes 3.4 secs.
[R 2.0.1 read in 23 secs using an additional 210Mb, and wrote
in 50 secs using an additional 450Mb.]
Will Frank Harrell or someone else please explain to me a
real application
in which this is not fast enough?
--
Brian D. Ripley, [EMAIL PROTECTED]
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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