| ppoints {stats} | R Documentation |
Ordinates for Probability Plotting
Description
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).
Usage
ppoints(n, a = ifelse(n <= 10, 3/8, 1/2))
Arguments
n |
either the number of points generate or a vector of observations. |
a |
the offset fraction to be used; typically in |
Details
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.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth \& Brooks/Cole.
See Also
qqplot, qqnorm.
Examples
ppoints(4) # the same as ppoints(1:4)
ppoints(10)
ppoints(10, a=1/2)