laplacian5PointsStencil

 The 5-points Laplacian stencil for arbitrary step sizes in X/Y
 
 Input:
   hx: grid step size in X (defaults to 1 if not set)
   hy: grid step size in Y (defaults to hx if not set)
 
 Output:
   stencil: the 3x3 5-points Laplacian stencil

0001 function stencil = laplacian5PointsStencil(hx, hy)
0002 % The 5-points Laplacian stencil for arbitrary step sizes in X/Y
0003 %
0004 % Input:
0005 %   hx: grid step size in X (defaults to 1 if not set)
0006 %   hy: grid step size in Y (defaults to hx if not set)
0007 %
0008 % Output:
0009 %   stencil: the 3x3 5-points Laplacian stencil
0010 %
0011 
0012 if nargin < 1
0013     hx = 1;
0014 end
0015 if nargin < 2
0016     hy = hx;
0017 end
0018 
0019 stencil = hx * [ 0 0 0; 1 -2 1; 0 0 0 ] + hy * [ 0 1 0; 0 -2 0; 0 1 0 ];