| % File src/library/base/man/jitter.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2011 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{jitter} |
| \alias{jitter} |
| \title{\sQuote{Jitter} (Add Noise) to Numbers} |
| \usage{ |
| jitter(x, factor = 1, amount = NULL) |
| } |
| \arguments{ |
| \item{x}{numeric vector to which \emph{jitter} should be added.} |
| \item{factor}{numeric.} |
| \item{amount}{numeric; if positive, used as \emph{amount} (see below), |
| otherwise, if \code{= 0} the default is \code{factor * z/50}. |
| |
| Default (\code{NULL}): \code{factor * d/5} where \code{d} is about |
| the smallest difference between \code{x} values.} |
| } |
| \description{ |
| Add a small amount of noise to a numeric vector. |
| } |
| \value{ |
| \code{jitter(x, \dots)} returns a numeric of the same length as |
| \code{x}, but with an \code{amount} of noise added in order to break |
| ties. |
| } |
| \details{ |
| The result, say \code{r}, is \code{r <- x + runif(n, -a, a)} |
| where \code{n <- length(x)} and \code{a} is the \code{amount} |
| argument (if specified). |
| |
| Let \code{z <- max(x) - min(x)} (assuming the usual case). |
| The amount \code{a} to be added is either provided as \emph{positive} |
| argument \code{amount} or otherwise computed from \code{z}, as |
| follows: |
| |
| If \code{amount == 0}, we set \code{a <- factor * z/50} (same as S). |
| |
| If \code{amount} is \code{NULL} (\emph{default}), we set |
| \code{a <- factor * d/5} where \emph{d} is the smallest |
| difference between adjacent unique (apart from fuzz) \code{x} values. |
| } |
| \references{ |
| Chambers, J. M., Cleveland, W. S., Kleiner, B. and Tukey, P.A. (1983) |
| \emph{Graphical Methods for Data Analysis.} Wadsworth; figures 2.8, |
| 4.22, 5.4. |
| |
| Chambers, J. M. and Hastie, T. J. (1992) |
| \emph{Statistical Models in S.} |
| Wadsworth & Brooks/Cole. |
| } |
| \author{Werner Stahel and Martin Maechler, ETH Zurich} |
| \seealso{ |
| \code{\link{rug}} which you may want to combine with \code{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)) |
| } |
| \keyword{dplot} |
| \keyword{utilities} |