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% Generated by roxygen2 (4.1.1): do not edit by hand
% Please edit documentation in R/scg.R
\name{stochastic_matrix}
\alias{get.stochastic}
\alias{stochastic_matrix}
\title{Stochastic matrix of a graph}
\usage{
stochastic_matrix(graph, column.wise = FALSE,
sparse = igraph_opt("sparsematrices"))
}
\arguments{
\item{graph}{The input graph. Must be of class \code{igraph}.}
\item{column.wise}{If \code{FALSE}, then the rows of the stochastic matrix
sum up to one; otherwise it is the columns.}
\item{sparse}{Logical scalar, whether to return a sparse matrix. The
\code{Matrix} package is needed for sparse matrices.}
}
\value{
A regular matrix or a matrix of class \code{Matrix} if a
\code{sparse} argument was \code{TRUE}.
}
\description{
Retrieves the stochastic matrix of a graph of class \code{igraph}.
}
\details{
Let \eqn{M} be an \eqn{n \times n}{n x n} adjacency matrix with real
non-negative entries. Let us define \eqn{D = \textrm{diag}(\sum_{i}M_{1i},
\dots, \sum_{i}M_{ni})}{D=diag( sum(M[1,i], i), ..., sum(M[n,i], i) )}
The (row) stochastic matrix is defined as \deqn{W = D^{-1}M,}{W = inv(D) M,}
where it is assumed that \eqn{D} is non-singular. Column stochastic
matrices are defined in a symmetric way.
}
\examples{
library(Matrix)
## g is a large sparse graph
g <- barabasi.game(n = 10^5, power = 2, directed = FALSE)
W <- stochastic_matrix(g, sparse=TRUE)
## a dense matrix here would probably not fit in the memory
class(W)
## may not be exactly 1, due to numerical errors
max(abs(rowSums(W))-1)
}
\author{
Gabor Csardi \email{csardi.gabor@gmail.com}
}
\seealso{
\code{\link{as_adj}}
}
\keyword{graphs}
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