R/laplacian.R

In HyperG: Hypergraphs in R

## HyperG R Package
## 
## Copyright (c) 2021 David J. Marchette <dmarchette@gmail.com>
## 
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## 


hypergraph_laplacian_matrix <- function(h,normalize=FALSE)
{
	
	if(is.empty.hypergraph(h)) {
		return(Matrix::Matrix(0,nrow=hsize(h),ncol=horder(h)))
	}
   A <- hypergraph_as_adjacency_matrix(h)
	d <- Matrix::rowSums(A)
	if(any(d==0)) {
	   j <- which(d==0)
		A <- A[-j,-j]
		d <- d[-j]
		warning("isolated vertex removed")
	}
	D <- Matrix::Diagonal(x=d)
	L <- D-A
	if(normalize){
		D2 <- Matrix::Diagonal(x=1/sqrt(d))
		L <- D2 %*% L %*% D2
	}
	L
}