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%% Sparse Laplacian Operator Matrix % This example visualizes a sparse Laplacian operator matrix. %% % The matrix representation of the discrete Laplacian operator on a % two-dimensional, |n|-by- |n| grid is a |n*n|-by- |n*n| sparse matrix. % There are at most five nonzero elements in each row or column. You can % generate the matrix as the Kronecker product of one-dimensional % difference operators. In this example |n = 5|. % Copyright 2015 The MathWorks, Inc. n = 5; I = speye(n,n); E = sparse(2:n,1:n-1,1,n,n); D = E+E'-2*I; A = kron(D,I)+kron(I,D); %% % Visualize the sparsity pattern with |spy|. spy(A,'k')