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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/games.R
\name{sample_pa_age}
\alias{sample_pa_age}
\alias{pa_age}
\title{Generate an evolving random graph with preferential attachment and aging}
\usage{
sample_pa_age(
n,
pa.exp,
aging.exp,
m = NULL,
aging.bin = 300,
out.dist = NULL,
out.seq = NULL,
out.pref = FALSE,
directed = TRUE,
zero.deg.appeal = 1,
zero.age.appeal = 0,
deg.coef = 1,
age.coef = 1,
time.window = NULL
)
pa_age(...)
}
\arguments{
\item{n}{The number of vertices in the graph.}
\item{pa.exp}{The preferential attachment exponent, see the details below.}
\item{aging.exp}{The exponent of the aging, usually a non-positive number,
see details below.}
\item{m}{The number of edges each new vertex creates (except the very first
vertex). This argument is used only if both the \code{out.dist} and
\code{out.seq} arguments are NULL.}
\item{aging.bin}{The number of bins to use for measuring the age of
vertices, see details below.}
\item{out.dist}{The discrete distribution to generate the number of edges to
add in each time step if \code{out.seq} is NULL. See details below.}
\item{out.seq}{The number of edges to add in each time step, a vector
containing as many elements as the number of vertices. See details below.}
\item{out.pref}{Logical constant, whether to include edges not initiated by
the vertex as a basis of preferential attachment. See details below.}
\item{directed}{Logical constant, whether to generate a directed graph. See
details below.}
\item{zero.deg.appeal}{The degree-dependent part of the
\sQuote{attractiveness} of the vertices with no adjacent edges. See also
details below.}
\item{zero.age.appeal}{The age-dependent part of the \sQuote{attrativeness}
of the vertices with age zero. It is usually zero, see details below.}
\item{deg.coef}{The coefficient of the degree-dependent
\sQuote{attractiveness}. See details below.}
\item{age.coef}{The coefficient of the age-dependent part of the
\sQuote{attractiveness}. See details below.}
\item{time.window}{Integer constant, if NULL only adjacent added in the last
\code{time.windows} time steps are counted as a basis of the preferential
attachment. See also details below.}
\item{...}{Passed to \code{sample_pa_age()}.}
}
\value{
A new graph.
}
\description{
This function creates a random graph by simulating its evolution. Each time
a new vertex is added it creates a number of links to old vertices and the
probability that an old vertex is cited depends on its in-degree
(preferential attachment) and age.
}
\details{
This is a discrete time step model of a growing graph. We start with a
network containing a single vertex (and no edges) in the first time step.
Then in each time step (starting with the second) a new vertex is added and
it initiates a number of edges to the old vertices in the network. The
probability that an old vertex is connected to is proportional to
\deqn{P[i] \sim (c\cdot k_i^\alpha+a)(d\cdot l_i^\beta+b)}.
Here \eqn{k_i}{k[i]} is the in-degree of vertex \eqn{i} in the current time
step and \eqn{l_i}{l[i]} is the age of vertex \eqn{i}. The age is simply
defined as the number of time steps passed since the vertex is added, with
the extension that vertex age is divided to be in \code{aging.bin} bins.
\eqn{c}, \eqn{\alpha}{alpha}, \eqn{a}, \eqn{d}, \eqn{\beta}{beta} and
\eqn{b} are parameters and they can be set via the following arguments:
\code{pa.exp} (\eqn{\alpha}{alpha}, mandatory argument), \code{aging.exp}
(\eqn{\beta}{beta}, mandatory argument), \code{zero.deg.appeal} (\eqn{a},
optional, the default value is 1), \code{zero.age.appeal} (\eqn{b},
optional, the default is 0), \code{deg.coef} (\eqn{c}, optional, the default
is 1), and \code{age.coef} (\eqn{d}, optional, the default is 1).
The number of edges initiated in each time step is governed by the \code{m},
\code{out.seq} and \code{out.pref} parameters. If \code{out.seq} is given
then it is interpreted as a vector giving the number of edges to be added in
each time step. It should be of length \code{n} (the number of vertices),
and its first element will be ignored. If \code{out.seq} is not given (or
NULL) and \code{out.dist} is given then it will be used as a discrete
probability distribution to generate the number of edges. Its first element
gives the probability that zero edges are added at a time step, the second
element is the probability that one edge is added, etc. (\code{out.seq}
should contain non-negative numbers, but if they don't sum up to 1, they
will be normalized to sum up to 1. This behavior is similar to the
\code{prob} argument of the \code{sample} command.)
By default a directed graph is generated, but it \code{directed} is set to
\code{FALSE} then an undirected is created. Even if an undirected graph is
generated \eqn{k_i}{k[i]} denotes only the adjacent edges not initiated by
the vertex itself except if \code{out.pref} is set to \code{TRUE}.
If the \code{time.window} argument is given (and not NULL) then
\eqn{k_i}{k[i]} means only the adjacent edges added in the previous
\code{time.window} time steps.
This function might generate graphs with multiple edges.
}
\examples{
# The maximum degree for graph with different aging exponents
g1 <- sample_pa_age(10000, pa.exp = 1, aging.exp = 0, aging.bin = 1000)
g2 <- sample_pa_age(10000, pa.exp = 1, aging.exp = -1, aging.bin = 1000)
g3 <- sample_pa_age(10000, pa.exp = 1, aging.exp = -3, aging.bin = 1000)
max(degree(g1))
max(degree(g2))
max(degree(g3))
}
\seealso{
Random graph models (games)
\code{\link{erdos.renyi.game}()},
\code{\link{sample_}()},
\code{\link{sample_bipartite}()},
\code{\link{sample_chung_lu}()},
\code{\link{sample_correlated_gnp}()},
\code{\link{sample_correlated_gnp_pair}()},
\code{\link{sample_degseq}()},
\code{\link{sample_dot_product}()},
\code{\link{sample_fitness}()},
\code{\link{sample_fitness_pl}()},
\code{\link{sample_forestfire}()},
\code{\link{sample_gnm}()},
\code{\link{sample_gnp}()},
\code{\link{sample_grg}()},
\code{\link{sample_growing}()},
\code{\link{sample_hierarchical_sbm}()},
\code{\link{sample_islands}()},
\code{\link{sample_k_regular}()},
\code{\link{sample_last_cit}()},
\code{\link{sample_pa}()},
\code{\link{sample_pref}()},
\code{\link{sample_sbm}()},
\code{\link{sample_smallworld}()},
\code{\link{sample_traits_callaway}()},
\code{\link{sample_tree}()}
}
\author{
Gabor Csardi \email{csardi.gabor@gmail.com}
}
\concept{games}
\keyword{graphs}
|
