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44 lines
1.2 KiB
44 lines
1.2 KiB
4 months ago
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import LuDecomposition from './dc/lu';
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import Matrix from './matrix';
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import MatrixSelectionView from './views/selection';
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export function determinant(matrix) {
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matrix = Matrix.checkMatrix(matrix);
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if (matrix.isSquare()) {
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if (matrix.columns === 0) {
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return 1;
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}
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let a, b, c, d;
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if (matrix.columns === 2) {
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// 2 x 2 matrix
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a = matrix.get(0, 0);
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b = matrix.get(0, 1);
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c = matrix.get(1, 0);
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d = matrix.get(1, 1);
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return a * d - b * c;
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} else if (matrix.columns === 3) {
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// 3 x 3 matrix
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let subMatrix0, subMatrix1, subMatrix2;
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subMatrix0 = new MatrixSelectionView(matrix, [1, 2], [1, 2]);
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subMatrix1 = new MatrixSelectionView(matrix, [1, 2], [0, 2]);
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subMatrix2 = new MatrixSelectionView(matrix, [1, 2], [0, 1]);
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a = matrix.get(0, 0);
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b = matrix.get(0, 1);
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c = matrix.get(0, 2);
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return (
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a * determinant(subMatrix0) -
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b * determinant(subMatrix1) +
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c * determinant(subMatrix2)
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);
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} else {
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// general purpose determinant using the LU decomposition
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return new LuDecomposition(matrix).determinant;
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}
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} else {
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throw Error('determinant can only be calculated for a square matrix');
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}
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}
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