| ppoints {stats} | R Documentation |
Generates the sequence of “probability” points
(1:m - a)/(m + (1-a)-a)
where m is either n, if length(n)==1, or
length(n).
ppoints(n, a = ifelse(n <= 10, 3/8, 1/2))
n |
either the number of points generated or a vector of observations. |
a |
the offset fraction to be used; typically in (0,1). |
If 0 < a < 1, the resulting values are within (0,1)
(excluding boundaries).
In any case, the resulting sequence is symmetric in [0,1], i.e.,
p + rev(p) == 1.
ppoints() is used in qqplot and qqnorm to generate
the set of probabilities at which to evaluate the inverse distribution.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
ppoints(4) # the same as ppoints(1:4) ppoints(10) ppoints(10, a=1/2)