R/DRW.R

In cuihaibo1/DRWPClass: DRW-GM

DRW <-
function(igraphM, p0, EdgeWeight=FALSE, gamma=0.3){
	if(EdgeWeight==TRUE){
		# convert igraph object to a weight matrix
		W <- get.adjacency(igraphM,attr="weight") 
	}
	if(EdgeWeight==FALSE){
		# convert igraph object to a conventional matrix
		W <- get.adjacency(igraphM) 
	}
	
	#Add Ground Node, construct new adjacent matrix
	newrow <- matrix(1,1,dim(W)[2])
	rownames(newrow) <- c("GN")
	W1 <- rBind(W,newrow)
	newcol <- matrix(1,dim(W1)[1],1)
	colnames(newcol) <- c("GN")
	WGN <- cBind(W1,newcol)   #adjacency matrix after adding ground node
		
	p0 <- t(as.matrix(p0/sum(p0)))
	# The initial probability of the ground node is 0.
	p0 <- cbind(p0,0)    
	colnames(p0)[dim(p0)[2]] = "GN"
		
	PT <- p0
	
	k <- 0
	delta <- 1
 	
	# reverse the direction of the edges
    WGN <- t(WGN)
	
	# normalization
	for (i in 1:dim(WGN)[1]){
		sumr <- sum(WGN[i,])
		if(sumr == 0){
			WGN[i,] <-numeric(length=length(WGN[i,]))
		}
		if(sumr > 0){
			WGN[i,] <- WGN[i,]/sumr
		}
	}
	WGN <- t(WGN)
	# iteration
	while(delta > 1e-10){
		PT1 <- (1-gamma)*WGN
		PT2 <- PT1 %*% t(PT)
		PT3 <- (gamma*p0)
		PT4 <- t(PT2) + PT3
		delta <- sum(abs(PT4 - PT))
		PT <- PT4
		k <- k + 1
	}
    PT <- t(PT)
	rownames(PT) <- NULL
	res <- PT[1:(dim(PT)[1]-1)]
	
	return(drop(res))
}