[Rd] chron vs. POSIX

From: Sebastian Luque <spluque_at_gmail.com>
Date: Fri 14 Jul 2006 - 19:38:54 GMT


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

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