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31 lines
968 B
31 lines
968 B
3 years ago
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%--------------------------
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% @Author: Jingqiao Hu
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% @Date: 2021-05-18 20:58:57
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% @LastEditTime: 2021-05-18 21:27:03
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% A : [9, m]
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%--------------------------
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function invA = inv_3rank(A)
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detA = det_3rank(A); % 1,m
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indicator = [(-1)^(1+1), (-1)^(1+2), (-1)^(1+3);
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(-1)^(1+2), (-1)^(2+2), (-1)^(3+2);
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(-1)^(1+3), (-1)^(2+3), (-1)^(3+3);];
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indicator = indicator(:); % 9,1
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M11 = A(5,:) .* A(9,:) - A(6,:) .* A(8,:);
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M12 = A(4,:) .* A(9,:) - A(6,:) .* A(7,:);
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M13 = A(4,:) .* A(8,:) - A(5,:) .* A(7,:);
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M21 = A(2,:) .* A(9,:) - A(3,:) .* A(8,:);
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M22 = A(1,:) .* A(9,:) - A(3,:) .* A(7,:);
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M23 = A(1,:) .* A(8,:) - A(2,:) .* A(7,:);
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M31 = A(2,:) .* A(6,:) - A(3,:) .* A(5,:);
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M32 = A(1,:) .* A(6,:) - A(3,:) .* A(4,:);
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M33 = A(5,:) .* A(1,:) - A(2,:) .* A(4,:);
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M = [M11; M12; M13; M21; M22; M23; M31; M32; M33];
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invA = detA .* (indicator .* M);
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end
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% 1,4,7
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% 2,5,8
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% 3,6,9
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