delsq, an Octave code which is given a grid G, and returns a corresponding sparse matrix D that defines the Laplacian operator on G.
Based on code that is copyright 1984-2015 The MathWorks, Inc.
delsq is available in a MATLAB version and an Octave version.
laplacian, an Octave code which carries out computations related to the discrete laplacian operator, including full or sparse evaluation, evaluation for unequally spaced data sampling points, application to data samples, solution of associated linear systems, eigenvalues and eigenvectors, and extension to 2D and 3D geometry.