ppoints

Bill Simpson wsimpson@uwinnipeg.ca
Thu, 3 Sep 1998 10:57:41 -0500 (CDT)


When I look at ppoints I see:

ppoints<-function (x) 
{
n <- length(x)
if (n == 1) 
	n <- x
(1:n - 0.5)/n
}

However Venables & Ripley (2nd ed, p 165) say ppoints() should return
(i-1/2)/n for n>=11; (i-3/8)/(n+1/4) for n<=10.

The version below should work as described:

ppoints<-function (x) 
{
n <- length(x)
if (n <= 10)
	(1:n - 0.375)/(n + 0.25) 
else
	(1:n - 0.5)/n
}

Bill Simpson

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