Crawley's book on S-Plus and one strangeness
matej at ceplovi.cz (Matej Cepl) writes:
I have got to my hands an excellent book by Michael J. Crawley ``Statistical Computing: An Introduction to Data Analysis using S-Plus'' (John Wiley & Sons, Ltd, ISBN 0-471-56040-5). Its beauty for me is in the fact, that it is more of ``An Introduction to Data Analysis'' than ``using S-Plus'', but I guess that it may be of interest for many others.
Most of the examples in the book are however taken from S-Plus and using datasets provided with it. Is there anywhere a copy of these datasets available for R?
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?
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.