\name{MultiGraph-class}
\Rdversion{1.1}
\docType{class}
\alias{MultiGraph-class}
\alias{nodes,MultiGraph-method}
\alias{numEdges,MultiGraph-method}
\alias{numEdges,MGEdgeSet-method}
\alias{numNodes,MultiGraph-method}
\alias{show,MultiGraph-method}
\alias{MultiGraph}
\alias{eweights}
\alias{edgeSetIntersect0}
\alias{subsetEdgeSets}
\alias{extractFromTo}
\alias{extractFromTo,MultiGraph-method}
\alias{extractGraphAM}
\alias{isDirected,MultiGraph-method}
\alias{ugraph,MultiGraph-method}
% these are not supposed to be publicly available
% but aliased here to quiet R CMD check
\alias{isDirected,DiEdgeSet-method}
\alias{isDirected,UEdgeSet-method}
\alias{ugraph,DiEdgeSet-method}
\alias{ugraph,UEdgeSet-method}

\title{EXPERIMENTAL class "MultiGraph"}
\description{

  The MultiGraph class represents a single node set and a set of edge
  sets.  Each edge set is either directed or undirected.  We can think
  of an edge in a MultiGraph as a 4-tuple (from-node, to-node,
  edge-type, weight), where the edge-type field in the tuple identifies
  the edge set, the weight is a numeric value, and the order of the
  nodes only matters in the case of a directed edge set.  Unlike some of
  the graph representations, self-loops are allowed (from-node ==
  to-node).

  There is support for arbitrary edge attributes which is primarily
  useful for rendering plots of MultiGraphs.  These attributes are
  stored separately from the edge weights to facilitate efficient edge
  weight computation.

}

\usage{
MultiGraph(edgeSets, nodes = NULL, directed = TRUE)
eweights(object, names.sep = NULL)
edgeSetIntersect0(g)
extractGraphAM(g, edgeSets)
}

\arguments{
  \item{edgeSets}{
    
    A named list of \code{data.frame} objects each representing an edge
    set of the multigraph.  Each \code{data.frame} must have three
    columns: "from", "to", and "weight".  Columns "from" and "to" can be
    either factors or character vectors.  The "weight" column must be
    numeric.

  }
  \item{nodes}{
    
    A character vector of node labels.  Nodes with zero degree can be
    included in a graph by specifying the node labels in \code{nodes}.
    The node set of the resulting multigraph is the union of the node
    labels found in \code{edgeSets} and \code{nodes}.

  }

  \item{directed}{

    A logical vector indicating whether the edge sets specified in
    \code{edgeSets} represent directed edges.  If this argument has
    length one, the value applies to all edge sets in \code{edgeSets}.
    Otherwise, this argument must have the same length as
    \code{edgeSets}, values are aligned by position.

  }

  \item{object}{
    A \code{MultiGraph} instance
  }

  \item{g}{
    A \code{MultiGraph} instance
  }

  \item{names.sep}{
    
    The string to use as a separator between from and to node labels.
    If \code{NULL} no names will be attached to the returned vector.
    
  }

}
\section{Constructors}{
  \code{MultiGraph}
}
\section{Methods}{
  \describe{

    \item{nodes}{Return the nodes of the multigraph.}

    \item{numEdges}{Return an integer vector named by edge set
      containing edge counts for each edge set.}

    \item{numNodes}{Return the number of nodes in the multigraph.}

    \item{eweights}{Return a list named by edge set; each element is a
      numeric vector of edge weights for the corresponding edge set.}

    \item{isDirected}{Return a logical vector named by the edge sets in
      \code{object} with a \code{TRUE} indicating a directed edge set
      and \code{FALSE} for undirected.}

    \item{extractFromTo}{Return a list named by the edge sets; each
      element is a data frame with column names from, to and weight
	  corresponding to the connected nodes in the edge set.}

    \item{subsetEdgeSets}{Return a new \code{MultiGraph} object 
	  representing the subset of edge sets from the original 
      \code{MultiGraph}.}

    \item{extractGraphAM}{Return a named \code{list} of \code{graphAM}
      objects corresponding to the edge sets from the original 
      \code{MultiGraph}.}

    \item{ugraph}{Return a new \code{MultiGraph} object in which all
      edge sets have been converted to undirected edge sets.  This
      operation sets all edge weights to one and drops other edge
      attributes.}

    \item{edgeSetIntersect0}{Return a new \code{MultiGraph} object
    representing the intersection of edges across all edge sets within
    \code{g}.  The return value will have zero edge sets if the edge
    sets in \code{g} are disjoint.  Otherwise, there will be a single
    edge set containing the shared edges.  The node set is preserved.
    Edge weights and edge attributes are dropped.}
   
    \item{show}{Prints a short summary of a MultiGraph object}
  }
}

\author{S. Falcon}

\examples{
    ft1 <- data.frame(from=c("a", "a", "a", "b", "b"),
                        to=c("b", "c", "d", "a", "d"),
                      weight=c(1, 3.1, 5.4, 1, 2.2))

    ft2 <- data.frame(from=c("a", "a", "a", "x", "x", "c"),
                        to=c("b", "c", "x", "y", "c", "a"),
                      weight=c(3.4, 2.6, 1, 1, 1, 7.9))

    esets <- list(es1=ft1, es2=ft2)

    g <- MultiGraph(esets)

    nodes(g)
    numEdges(g)

    eweights(g)
    eweights(g, names.sep = "=>")
    isDirected(g)
    ug <- ugraph(g)
    isDirected(ug)
    numEdges(ug)
    edgeSetIntersect0(g)
    subsetEdgeSets(g, "es1")
    extractFromTo(g)
    extractGraphAM(g)
    extractGraphAM(g, "es1")
}
\keyword{classes}