25 lines
646 B
Mathematica
25 lines
646 B
Mathematica
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function [A,xy] = grid5recRotate(k1, k2, angle)
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% GRID5lrec : Generate 5-point finite difference on a rectangular mesh.
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%
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% [A,xy] = GRID5REC(k) returns a k1*k2-by-k1*k2 symmetric positive definite
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% matrix A with the structure of the k-by-k 5-point grid,
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% and an array xy of coordinates for the grid points.
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a = blockdiags ([-1 4 -1], -1:1, k1, k1);
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I = speye (k1, k1);
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A = blockdiags ([-I a -I], -1:1, k2, k2);
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A = diag(diag(A)) - A;
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[x,y] = meshgrid(1:k2, 1:k1);
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rad = angle*pi/180;
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newX = x * cos(rad) - y * sin(rad);
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newY = y * cos(rad) + x * sin(rad);
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xy = zeros(k1*k2,2);
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xy(:,1) = newX(:);
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xy(:,2) = newY(:);
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end
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