ppoints {base} | 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))
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.
ppoints(4) # the same as ppoints(1:4) ppoints(10) ppoints(10, a=1/2)