jitter {base} | R Documentation |

## Add 'Jitter' (Noise) to Numbers

### Description

Add a small amount of noise to a numeric vector.

### Usage

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

### Arguments

`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. |

### Details

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.

### Value

`jitter(x,...)`

returns a numeric of the same length as
`x`

, but with an `amount`

of noise added in order to break
ties.

### Author(s)

Werner Stahel and Martin Maechler, ETH Zurich

### References

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`

.

### Examples

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))

[Package

*base* version 2.2.1

Index]