| jitter {base} | R Documentation |
Add a small amount of noise to a numeric vector.
jitter(x, factor=1, amount = NULL)
x |
numeric to which jitter should be added. |
factor |
numeric |
amount |
numeric; if positive, used as amount (see below),
otherwise, if = 0 the default is factor * z/50.
Default ( NULL): factor * d/5 where d is about
the smallest difference between x values. |
The result, say r, is r <- x + runif(n, -a, a)
where n <- length(x) and a is the amount
argument (if specified).
Let z <- max(x) - min(x) (assuming the usual case).
The amount a to be added is either provided as positive
argument amount or otherwise computed from z, as
follows:
If amount == 0, we set a <- factor * z/50 (same as S).
If amount is NULL (default), we set
a <- factor * d/5 where d is the smallest
difference between adjacent unique (apart from fuzz) x values.
jitter(x,...) returns a numeric of the same length as
x, but with an amount of noise added in order to break
ties.
Werner Stahel and Martin Maechler, ETH Zurich
Chambers, J. M., Cleveland, W. S., Kleiner, B. and Tukey, P.A. (1983) Graphical Methods for Data Analysis. Wadsworth; figures 2.8, 4.22, 5.4.
Chambers, J. M. and Hastie, T. J. (1992) Statistical Models in S. Wadsworth & Brooks/Cole.
rug which you may want to combine with jitter.
round(jitter(c(rep(1,3), rep(1.2, 4), rep(3,3))), 3) ## These two 'fail' with S-plus 3.x: jitter(rep(0, 7)) jitter(rep(10000,5))