\name{shapley}
\alias{shapley}
\alias{shapley.extra}
\docType{data}
\title{Galaxies in the Shapley Supercluster}
\description{
  A point pattern recording the sky positions of 4215 galaxies
  in the Shapley Supercluster.
} 
\format{
  \code{shapley} is an object of class \code{"ppp"}
  representing the point pattern of galaxy locations
  (see \code{\link[spatstat]{ppp.object}}).

  \code{shapley.extra} is a list containing additional data
  described under Notes.
}
\usage{data(shapley)}
\examples{
  data(shapley)
  if(require(spatstat)) {
  shapley.extra$plotit(main="Shapley Supercluster")
  }
}
\source{M.J. Drinkwater, Department of Physics, University of
  Queensland}
\section{Notes}{
  This dataset comes from a survey by Drinkwater et al (2004) 
  of the Shapley Supercluster, one of the most massive concentrations
  of galaxies in the local universe. The data give the sky positions
  of 4215 galaxies observed using the FLAIR-II spectrograph
  on the UK Schmidt Telescope (UKST). They were kindly provided by
  Dr Michael Drinkwater through the Centre for Astrostatistics
  at Penn State University.

  Sky positions are given using the coordinates
  Right Ascension (degrees from 0 to 360) and
  Declination (degrees from -90 to 90).
  
  The point pattern has three mark variables:
  \describe{
    \item{Mag}{
      Galaxy magnitude (a negative logarithmic measure of
      visible brightness).
    }
    \item{V}{
      Recession velocity (km/sec) inferred from redshift,
      with corrections applied.
    }
    \item{SigV}{
      Estimated standard error for \code{V}.
    }
  }
  The region covered by the survey was approximately the
  UKST's standard quadrilateral survey fields 382 to 384 and 443 to 446.
  However, a few of the galaxy positions lie outside these fields.

  The point pattern dataset \code{shapley} consists of all 4215 galaxy
  locations. The observation window for this pattern is a
  dilated copy of the convex hull of the galaxy positions,
  constructed so that all galaxies lie within the window.

  Note that the data contain duplicated points (two points at the
  same location). To determine which points are duplicates,
  use \code{\link[spatstat]{duplicated.ppp}}.
  To remove the duplication, use \code{\link[spatstat]{unique.ppp}}.

  The auxiliary dataset \code{shapley.extra} contains 
  the following components:
  \describe{
    \item{\code{UKSTfields}}{
      a list of seven windows
      (objects of class \code{"owin"}) giving the UKST standard survey
      fields.
    }
    \item{\code{UKSTdomain}}{
      the union of these seven fields,
      an object of class \code{"owin"}.
    }
    \item{\code{plotit}}{
      a function (called without arguments)
      that will plot the data and the survey fields
      in the conventional astronomical presentation,
      in which Right Ascension is converted
      to hours and minutes (1 hour equals 15 degrees) and 
      Right Ascension decreases as we move to the right of the plot.
    }
  }
}
\references{
  Drinkwater, M.J., Parker, Q.A., Proust, D., Slezak, E.
  and Quintana, H. (2004)
  The large scale distribution of galaxies in the Shapley
  Supercluster.
  \emph{Publications of the Astronomical Society of Australia}
  \bold{21}, 89-96. \code{DOI 10.1071/AS03057}
} 
\keyword{datasets}
\keyword{spatial}

