C++_eigen function Library Usage Note--advanced initialization

• The comma initializer
  • a simple example  
  • Join and Block initialize
    • Join, Row vectors together
    • Initialize metrics with block structure
    • Fill block expression
• Special metrics and arrays
  • Zero ();
    • Array33f::zero ();
    • Arrayxf::zero (3);
    • Arrayxxf::zero (3,4);
  • Constant (Rows,cols,value);
  • Identity ();
  • linspaced
  • 3 ways to construct the matrix
• Usage as temporary objects

   

1. The comma initializer
   2. a simple example matrix3f m;m << 1, 2, 3,4, 5, 6,7, 8, 9;std::cout << m;
   3. Join and Block initialize
      • Join, Row vectors togetherrowvectorxd vec1 (3), VEC1 << 1, 2, 3;std::cout << "VEC1 =" << vec1 << Std::endl; Rowvectorxd VEC2 (4); vec2 << 1, 4, 9, 16;; Std::cout << "vec2 =" << vec2 << Std::endl; Rowvectorxd joined (7); joined << VEC1, vec2;std::cout << "joined =" << joined << STD::ENDL;VEC1 = 1 2 3
        VEC2 = 1 4 9 16
        Joined = 1 2 3 1 4 9 16
      • Initialize metrics with block STRUCTUREMATRIXXF MatA (2, 2); MatA << 1, 2, 3, 4;  MATRIXXF MATB (4, 4); MATB << MatA, MATA/10, MATA/10, mata;std::cout << MATB << Std::endl; 1 2 0.1 0.2
        3 4 0.3 0.4
        0.1 0.2 1 2
        0.3 0.4 3 4
      • Fill Block expressionmatrix3f m;m.row (0) << 1, 2, 3;m.block (1,0,2,2) << 4, 5, 7, 8;m.col (2). Tail (2) << 6 , 9;std::cout << m;1 2 3
        4 5 6
        7 8 9
2. special metrics and Arrays
   2. Zero ()
      • Array33f::zero ();
      • Arrayxf::zero (3);
      • Arrayxxf::zero (3,4); Std::cout << "A fixed-size array:\n"; array33f a1 = Array33f::zero () std::cout << A1 << "\ n"; std::cout << "A one-dimensional dynamic-size ar Ray:\n "; ARRAYXF A2 = Arrayxf::zero (3) std::cout << A2 << "\ n"; std::cout << "A two-dimensional dynamic-size arr Ay:\n "; ARRAYXXF a3 = Arrayxxf::zero (3, 4); Std::cout << A3 << "\ n"; A fixed-size Array:
        0 0 0
        0 0 0
        0 0 0
        
        A one-dimensional dynamic-size array:
        0
        0
        0
        
        A two-dimensional dynamic-size array:
        0 0 0 0
        0 0 0 0
        0 0 0 0
   4. Constant (Rows,cols,value);
   6. Identity ();
   7. linspacedARRAYXXF table (4), Table.col (0) = arrayxf::linspaced (0,), Table.col (1) = m_pi/180 * Table.col (0); Table.col (2) = Table.col (1). Sin (); Table.col (3) = Table.col (1). cos (); std::cout << "Degrees Radians Sine cosine\n"; Std::cout < < table << Std::endl;degrees Radians Sine cosine
      0 0 0 1
      10 0.175 0.174 0.985
      20 0.349 0.342 0.94
      30 0.524 0.5 0.866
      40 0.698 0.643 0.766
      50 0.873 0.766 0.643
      60 1.05 0.866 0.5
      70 1.22 0.94 0.342
      80 1.4 0.985 0.174
      1.57 1-4.37e-08
   8. 3 ways to construct the matrixconst int size = 6; Matrixxd mat1 (size, size), Mat1.topleftcorner (SIZE/2, SIZE/2) = Matrixxd::zero (SIZE/2, SIZE/2); Mat1.toprightcorner ( SIZE/2, SIZE/2) = Matrixxd::identity (SIZE/2, SIZE/2); Mat1.bottomleftcorner (SIZE/2, SIZE/2) = MatrixXd::Identity (size/ 2, SIZE/2); Mat1.bottomrightcorner (SIZE/2, SIZE/2) = Matrixxd::zero (SIZE/2, SIZE/2); std::cout << MAT1 << std :: Endl << Std::endl; Matrixxd mat2 (size, size), Mat2.topleftcorner (SIZE/2, SIZE/2). Setzero (); Mat2.toprightcorner (SIZE/2, SIZE/2). Setidentity (); Mat2.bottomleftcorner (SIZE/2, SIZE/2). setidentity (); Mat2.bottomrightcorner (SIZE/2, SIZE/2). SetZero (); Std::cout << mat2 << std::endl << Std::endl; Matrixxd MAT3 (size, size), MAT3 << Matrixxd::zero (SIZE/2, SIZE/2), Matrixxd::identity (SIZE/2, SIZE/2), Matrixxd: : Identity (SIZE/2, SIZE/2), Matrixxd::zero (SIZE/2, SIZE/2);std::cout << mat3 <<  Std::endl;

      0 0 0 1 0 00 0 0 0 1 00 0 0 0 0 11 0 0 0 0 00 1 0 0 0 00 0 1 0 0 00 0 0 1 0 00 0 0 0 1 00 0 0 0 0 11 0 0 0 0 00 0 1 0 0 00 0 0 1 0 00 0 0 0 1 00 0 0 0 0 11 0 0 0 0 00 1 0 0 0 00 0 1 0 0 0

       
4. Usage as temporary objects MATRIXXF mat = Matrixxf::random (2, 3), Std::cout << mat << std::endl << Std::endl;mat = (MATRIXXF (2,2) &L t;< 0, 1, 1, 0). Finished () * Mat;std::cout << mat << Std::endl; 0.68 0.566 0.823
   -0.211 0.597-0.605
   
   -0.211 0.597-0.605
   0.68 0.566 0.823

The finished () method is necessary this actual matrix object once the comma initialization of our temporary Submatrix is done.

C++_eigen function Library Usage Note--advanced initialization