Prof Brian Ripley
Prof Brian Ripley <firstname.lastname@example.org>
Thu, 3 Sep 1998 18:05:43 +0100 (BST)
> Date: Thu, 3 Sep 1998 18:29:06 +0200
> From: Martin Maechler <email@example.com>
> To: Bill Simpson <firstname.lastname@example.org>
> CC: Remail@example.com
> Subject: Re: ppoints
> Thank you, Bill, for raising this point!
> However, if changing ppoints(.) for compatibility
> we should do it properly.
> e.g., the case
> should give the same as
> Also, S has the much nicer extra argument 'a' with the default
> a <- if(n > 10) 0.5 else 0.375
> which leads to the behavior you cite below.
> Maybe the S authors would forgive us we just used S' version ppoints()?
> (it's S, not S-plus!)
I just sent privately:
ppoints <- function (n, a = ifelse(n <= 10, 3/8, 1/2))
if(length(n) > 1) n <- length(n)
(1:n - a)/(n + (1-a) - a)
which is I believe fully compatible with S (except for the mode of the
length-0 result) and not the same code as S as I wrote it by reading
S's help page. (I know you can simplify the denominator, but I am
trying to explain the formula.)
Brian D. Ripley, firstname.lastname@example.org
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: email@example.com