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37 lines
1.4 KiB
C++
37 lines
1.4 KiB
C++
#include <Eigen/Core>
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USING_PART_OF_NAMESPACE_EIGEN
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using namespace std;
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int main(int, char **)
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{
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Matrix<double,2,2> m; // 2x2 fixed-size matrix with uninitialized entries
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m(0,0) = 1;
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m(0,1) = 2;
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m(1,0) = 3;
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m(1,1) = 4;
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cout << "Here is a 2x2 matrix m:" << endl << m << endl;
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cout << "Let us now build a 4x4 matrix m2 by assembling together four 2x2 blocks." << endl;
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MatrixXd m2(4,4); // dynamic matrix with initial size 4x4 and uninitialized entries
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// notice how we are mixing fixed-size and dynamic-size types.
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cout << "In the top-left block, we put the matrix m shown above." << endl;
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m2.block<2,2>(0,0) = m;
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cout << "In the bottom-left block, we put the matrix m*m, which is:" << endl << m*m << endl;
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m2.block<2,2>(2,0) = m * m;
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cout << "In the top-right block, we put the matrix m+m, which is:" << endl << m+m << endl;
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m2.block<2,2>(0,2) = m + m;
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cout << "In the bottom-right block, we put the matrix m-m, which is:" << endl << m-m << endl;
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m2.block<2,2>(2,2) = m - m;
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cout << "Now the 4x4 matrix m2 is:" << endl << m2 << endl;
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cout << "Row 0 of m2 is:" << endl << m2.row(0) << endl;
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cout << "The third element in that row is " << m2.row(0)[2] << endl;
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cout << "Column 1 of m2 is:" << endl << m2.col(1) << endl;
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cout << "The transpose of m2 is:" << endl << m2.transpose() << endl;
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cout << "The matrix m2 with row 0 and column 1 removed is:" << endl << m2.minor(0,1) << endl;
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return 0;
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}
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