The R Project SVN R

% File src/library/grDevices/man/pretty.Date.Rd
% Part of the R package, http://www.R-project.org
% Copyright 2010 R Core Team
% Distributed under GPL 2 or later

\name{pretty.Date}
\title{Pretty Breakpoints for Date-Time Classes}
\alias{pretty.Date}
\alias{pretty.POSIXt}
\usage{
\method{pretty}{Date}(x, n = 5, min.n = n \%/\% 2, sep = " ", \dots)
\method{pretty}{POSIXt}(x, n = 5, min.n = n \%/\% 2, sep = " ", \dots)
}
\arguments{
  \item{x}{an object of class \code{"Date"} or \code{"POSIXt"} (i.e.,
    \code{"POSIXct"} or \code{"POSIXlt"}). }
  \item{n}{integer giving the \emph{desired} number of
    intervals.  }
  \item{min.n}{nonnegative integer giving the \emph{minimal} number of
    intervals.  }
  \item{sep}{character string, serving as a separator for certain
    formats (e.g., between month and year). }
  \item{\dots}{further arguments for compatibility with the generic,
    ignored.}
}
\description{
  Compute a  sequence of about \code{n+1} equally spaced \sQuote{nice}
  values which cover the range of the values in \code{x}.
}
\value{
  A vector (of the suitable class) of locations, with attribute
  \code{"labels"} giving corresponding formatted character labels.
}
\seealso{
  \code{\link{pretty}} for the default method.
}
\examples{

steps <-
    list("10 secs", "1 min", "5 mins", "30 mins", "6 hours", "12 hours",
         "1 DSTday", "2 weeks", "1 month", "6 months", "1 year",
         "10 years", "50 years", "1000 years")

names(steps) <- paste("span =", unlist(steps))

x <- as.POSIXct("2002-02-02 02:02")
lapply(steps,
       function(s) {
           at <- pretty(seq(x, by = s, length = 2), n = 5)
           attr(at, "labels")
       })

}
\keyword{dplot}