jitter {base}R Documentation

Add 'Jitter' (Noise) to Numbers


Add a small amount of noise to a numeric vector.


jitter(x, factor=1, amount = NULL)


x numeric vector 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.

See Also

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))

[Package base version 2.5.0 Index]