3.9.5.4 Eigenvalues and Eigenvectors

Real Symmetric Matrix Eigenproblem(Origin8 SR1)

#include <Origin.h>
////////////////////////////////////////////////////////////////////////////////////


////////////////////////////////////////////////////////////////////////////////////
// Include your own header files here.
#define NMAX1 4
#define TDA1 NMAX1
#define TDV1 NMAX1
 
 
 
void real_symmetric_matrix_eigenproblem()
{
  Integer  i, j, n;
  double a[NMAX1*TDA1], r[NMAX1], v[NMAX1*TDV1];
 
  n = 4;  // assume that NMAX1 is larger than n
  matrix mx = {{0.5,0.0,2.3,-2.6},{0.0,0.5,-1.4,-0.7},{2.3,-1.4,0.5,0.0},{ -2.6,-0.7,0.0,0.5}};
 
 
  //f02abc(n, (double *)a, (Integer)TDA1, r, (double *)v, (Integer)TDV1,
         //NAGERR_DEFAULT);
 
  f02abc(n, (double *)mx, n, r, (double *)v, n,
         NAGERR_DEFAULT);
 
  printf("Eigenvalues\n");
  for (i=0; i<n; i++)
    printf("%9.4f ", r[i]);
  printf("\n");
 
  printf("Eigenvectors\n");
  for ( i=0; i<n; i++)
  {
      for (j=0; j<n; j++)
      printf("%9.4f ", v[i*n+j]);
      printf("\n");
  }
 
}

#include <Origin.h>
////////////////////////////////////////////////////////////////////////////////////


////////////////////////////////////////////////////////////////////////////////////
// Include your own header files here.
#include <OC_nag.h>

#define NMAX2 10
#define TDA2 NMAX2
#define TDV2 NMAX2

void real_symmetric_matrix_eigenproblem_ex2()
{
  Integer  i, j, n;
  double r[NMAX2], v[NMAX2*TDV2];
  
  // get input matrix data from a matrix layer
  MatrixLayer ml = Project.ActiveLayer();
  Matrix mData(ml);// Get the active Matrix from a MatrixLayer
  n = mData.GetNumRows();  // assume that NMAX is larger than n
  ASSERT(mData.GetNumRows()==GetNumCols());
  
  
  f02abc(n, (double *)mData, n, r, (double *)v, n,
         NAGERR_DEFAULT);
         
  printf("Eigenvalues\n");
  for (i=0; i<n; i++)
    printf("%9.4f ", r[i]);
  printf("\n");
  
  printf("Eigenvectors\n");
  for ( i=0; i<n; i++)
  {
  	  for (j=0; j<n; j++)
      printf("%9.4f ", v[i*n+j]);
  	  printf("\n");
  }
  
}

Real Matrix Eigenproblem(Origin8 SR1)

#include <Origin.h>
////////////////////////////////////////////////////////////////////////////////////


////////////////////////////////////////////////////////////////////////////////////
// Include your own header files here.
#include <OC_nag.h>

void general_real_matrix_eigenproblem()
{
  Integer  i, j, n;

// for a general real matrix, its eigenvalues and eigenvector may be complex
// so use complex matrix to store the result       	
  matrix<complex> r, v;
  r.SetSize(1,4);
  v.SetSize(4,4);
  Integer iter[4];
  matrix a = {{1.5,0.1,4.5,-1.5},{-22.5,3.5,12.5,-2.5},{-2.5,0.3,4.5,-2.5},{-2.5,0.1,4.5,2.5}};
  n = 4;

  f02agc(n, a, n, r, v,
         n, iter, NAGERR_DEFAULT);
         
   printf("Eigenvalues\n");
   for (i=0; i<n; i++)
   {
  	complex temp = r[0][i];
  	printf("(%7.3f, %7.3f) \n", temp.m_re, temp.m_im);
   }
    
   printf("\nEigenvectors\n");
   for (i=0; i<n; i++)
    for (j=0; j<n; j++)
      {
	complex temp = v[i][j];
	printf("(%7.3f, %7.3f)", temp.m_re, temp.m_im);
	if(j%4==3 || j==n-1)
	 printf("\n");	
      }  
}