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# IGraph R package
# Copyright (C) 2005-2012 Gabor Csardi <csardi.gabor@gmail.com>
# 334 Harvard street, Cambridge, MA 02139 USA
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA
#
###################################################################
#' Cocitation coupling
#'
#' Two vertices are cocited if there is another vertex citing both of them.
#' \code{cocitation} siply counts how many types two vertices are cocited. The
#' bibliographic coupling of two vertices is the number of other vertices they
#' both cite, \code{bibcoupling} calculates this.
#'
#' \code{cocitation} calculates the cocitation counts for the vertices in the
#' \code{v} argument and all vertices in the graph.
#'
#' \code{bibcoupling} calculates the bibliographic coupling for vertices in
#' \code{v} and all vertices in the graph.
#'
#' Calculating the cocitation or bibliographic coupling for only one vertex
#' costs the same amount of computation as for all vertices. This might change
#' in the future.
#'
#' @aliases cocitation bibcoupling
#' @param graph The graph object to analyze
#' @param v Vertex sequence or numeric vector, the vertex ids for which the
#' cocitation or bibliographic coupling values we want to calculate. The
#' default is all vertices.
#' @return A numeric matrix with \code{length(v)} lines and
#' \code{vcount(graph)} columns. Element \code{(i,j)} contains the cocitation
#' or bibliographic coupling for vertices \code{v[i]} and \code{j}.
#' @author Gabor Csardi \email{csardi.gabor@@gmail.com}
#' @export
#' @keywords graphs
#' @examples
#'
#' g <- make_ring(10)
#' cocitation(g)
#' bibcoupling(g)
#'
cocitation <- function(graph, v=V(graph)) {
if (!is_igraph(graph)) {
stop("Not a graph object")
}
v <- as.igraph.vs(graph, v)
on.exit( .Call(C_R_igraph_finalizer) )
res <- .Call(C_R_igraph_cocitation, graph, v-1)
if (igraph_opt("add.vertex.names") && is_named(graph)) {
rownames(res) <- vertex_attr(graph, "name", v)
colnames(res) <- vertex_attr(graph, "name")
}
res
}
#' @export
bibcoupling <- function(graph, v=V(graph)) {
if (!is_igraph(graph)) {
stop("Not a graph object")
}
v <- as.igraph.vs(graph, v)
on.exit( .Call(C_R_igraph_finalizer) )
res <- .Call(C_R_igraph_bibcoupling, graph, v-1)
if (igraph_opt("add.vertex.names") && is_named(graph)) {
rownames(res) <- vertex_attr(graph, "name", v)
colnames(res) <- vertex_attr(graph, "name")
}
res
}
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