Crawley's book on S-Plus and one strangeness

Can you be more specific?  Which datasets?

And one small question aside: I was very much surprised (in this
book as well as on this list) how many times people use
sqrt(var(x)) when what they want to say (IMHO) is sd(x). Is it
just a macho way to show that I understand more complicated
things, or is there any real difference between the two?

There is a big number of them (the book has 761 pages and no CD,
so all data used are I suppose from S-Plus), but let's make
a couple of examples:

	* blowfly -- ``The Australian ecologist A.J.Nicholson reared
	  blofly larvae on pieces of liver in laboratory culture for
	  almost 7 years'' ... used for analysis of cyclicity and acf
	  function,
	* rats -- data from Sokal and Rohlf (1995) describing an
	  experiment with three treatments to six rats; used for ANOVA
	* regression -- weight of caterpillars relates to the tannin
	  content of their diet
	* etc. I really do not think, that six pages long list makes
	  any difference.

The var function was available in S long before the sd function was
introduced and many 'old-timers' instinctively use sqrt(var(x)) rather
than sd(x).  The sd function ends up calling sqrt(var(x, na.rm =
na.rm)) when argument x is a vector.

I see.

Matej

Matej Cepl, matej at ceplovi.cz,
Finger: 89EF 4BC6 288A BF43 1BAB  25C3 E09F EF25 D964 84AC
138 Highland Ave. #10, Somerville, Ma 02143, (617) 623-1488
 
The law, in its majestic equality, forbids the rich as well as
the poor to sleep under bridges, to beg in the streets, and to
steal bread.
    -- Anatole France