% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/community.R
\name{contract}
\alias{contract}
\title{Contract several vertices into a single one}
\usage{
contract(graph, mapping, vertex.attr.comb = igraph_opt("vertex.attr.comb"))
}
\arguments{
\item{graph}{The input graph, it can be directed or undirected.}

\item{mapping}{A numeric vector that specifies the mapping. Its elements
correspond to the vertices, and for each element the id in the new graph is
given.}

\item{vertex.attr.comb}{Specifies how to combine the vertex attributes in
the new graph. Please see \code{\link[=attribute.combination]{attribute.combination()}} for details.}
}
\value{
A new graph object.
}
\description{
This function creates a new graph, by merging several vertices into one. The
vertices in the new graph correspond to sets of vertices in the input graph.
}
\details{
The attributes of the graph are kept. Graph and edge attributes are
unchanged, vertex attributes are combined, according to the
\code{vertex.attr.comb} parameter.
}
\section{Related documentation in the C library}{
\href{https://igraph.org/c/html/0.10.17/igraph-Operators.html#igraph_contract_vertices}{\code{contract_vertices()}}
}

\examples{

g <- make_ring(10)
g$name <- "Ring"
V(g)$name <- letters[1:vcount(g)]
E(g)$weight <- runif(ecount(g))

g2 <- contract(g, rep(1:5, each = 2),
  vertex.attr.comb = toString
)

## graph and edge attributes are kept, vertex attributes are
## combined using the 'toString' function.
print(g2, g = TRUE, v = TRUE, e = TRUE)

}
\seealso{
Other functions for manipulating graph structure: 
\code{\link{+.igraph}()},
\code{\link{add_edges}()},
\code{\link{add_vertices}()},
\code{\link{complementer}()},
\code{\link{compose}()},
\code{\link{connect}()},
\code{\link{delete_edges}()},
\code{\link{delete_vertices}()},
\code{\link{difference}()},
\code{\link{difference.igraph}()},
\code{\link{disjoint_union}()},
\code{\link{edge}()},
\code{\link{igraph-minus}},
\code{\link{intersection}()},
\code{\link{intersection.igraph}()},
\code{\link{path}()},
\code{\link{permute}()},
\code{\link{rep.igraph}()},
\code{\link{reverse_edges}()},
\code{\link{simplify}()},
\code{\link{transitive_closure}()},
\code{\link{union}()},
\code{\link{union.igraph}()},
\code{\link{vertex}()}
}
\author{
Gabor Csardi \email{csardi.gabor@gmail.com}
}
\concept{functions for manipulating graph structure}
\keyword{graphs}
