[Rd] chron vs. POSIX

Sebastian Luque spluque at gmail.com
Fri Jul 14 21:38:54 CEST 2006


One of the big decisions when writing code is how to handle dates and
times.  Gabor Grothendieck provided an excellent overview of the issue in
his R News 4/1 (2004) article, and many users and developers are probably
using it as a guide.  The proposed guideline is to use the simplest class
required; as Gabor put it "use Date if possible, otherwise use chron, and
otherwise use POSIX".

This seems to me a very efficient strategy, judging from my own
experiences and those of others users.  All but the simplest calculations
with POSIX objects demand great care, due to time zone and and daylight
savings considerations.  Therefore, I've always chosen chron for
relatively complex projects, where I don't need to deal with time zones or
daylight savings problems.  The ease with which objects can be switched
from numeric to chron representations is a major advantage IMHO¹.

If Gabor's recommendations are to be followed, wouldn't it make sense to
include chron in base R?  Given that flexibility for handling time
variables is so fundamental, the addition of chron to base R would provide
users everything they need to work with time, without the need to rely on
an external package.  What do others think?

+---- *Footnotes* ----+
¹ This is possible with POSIX classes too by using the structure()
  function, but a post by Brian Ripley to the effect that it may not be
  practical in the long term further convinced me of this.

Sebastian P. Luque
Department of Biology
Memorial University of Newfoundland
sluque at mun.ca

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