On Wed, 8 Oct 2008, Erin Hodgess wrote:
Hi R People:
I am looking at the Braun/Murdoch book, " A First Course in
Statistical Programming in R", and I have a question about a function
there. It's on page 52, Example 4.5; the sieve of Erastosthenes.
There is a line:
primes <- c()
Is there a difference between using that and
primes <- NULL
please?
When you put in primes <- c(), primes comes back as NULL.
Is one more efficient or is this just a matter of programming style, please?
What would be more efficient is primes <- integer(0) (as it looks like
'primes' concatenates integer vectors, at a quick glance).
Use a function call c() to get NULL is not efficient, but all the
differences here are tiny.
Thanks in advance,
Sincerely,
Erin
--
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: [EMAIL PROTECTED]
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--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
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Oxford OX1 3TG, UK Fax: +44 1865 272595
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