Application ou QR décomposition


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c00k.c
/* ------------------------------------ */
/*  Save as :   c00k.c                   */
/* ------------------------------------ */
#include "v_a.h"
/* ------------------------------------ */
/* ------------------------------------ */
#define   RA R5
#define   CA C5
#define   Cb C1 
/* ------------------------------------ */
/* ------------------------------------ */
void fun(void)
{
double ab[RA*(CA+Cb)]={
/* x**0   x**1   x**2    x**3    x**4    y  */
   1,     1.,    1.,      1.,      1.,  -5.,
   1,     2.,    4.,      8.,     16.,   8.,
   1,     3.,    9.,     27.,     81.,  -7.,
   1,     4.,   16.,     64.,    256.,   1.,
   1,     5.,   25.,    125.,    625.,  -4.,
};

double **Ab = ca_A_mR(ab,i_Abr_Ac_bc_mR(RA,CA,Cb));
double **A  = c_Ab_A_mR(Ab,i_mR(RA,CA));
double **b  = c_Ab_b_mR(Ab,i_mR(RA,Cb));

double **Q    = i_mR(RA,CA);
double **R    = i_mR(CA,CA);

double **invR = i_mR(CA,CA);
double **Q_T  = i_mR(CA,RA);


double **invR_Q_T = i_mR(CA,RA);
double **x        = i_mR(CA,Cb); // x invR * Q_T * b

  clrscrn();
  printf(" Fitting a quartic equation Curve to Data :\n\n");
  printf(" A :");
  p_mR(A,S7,P2,C7);
  printf(" b :");
  p_mR(b,S7,P2,C7);
  printf(" Ab :");
  p_mR(Ab,S7,P2,C7);
  stop();
    
  clrscrn();
  QR_mR(A,Q,R);    
  printf(" Q :");
  p_mR(Q,S10,P4,C6);  
  printf(" R :");
  p_mR(R,S10,P4,C6);
  stop();

  clrscrn();
  transpose_mR(Q,Q_T);   
  printf(" Q_T :");
  pE_mR(Q_T,S7,P4,C6); 
  inv_mR(R,invR); 
  printf(" invR :");
  pE_mR(invR,S7,P4,C6);
  stop();
  
  clrscrn();
  printf(" Solving this system yields a unique\n"
         " least squares solution, namely   \n\n");
  mul_mR(invR,Q_T,invR_Q_T);
  mul_mR(invR_Q_T,b,x);
  printf(" x = invR * Q_T * b :");
  p_mR(x,S10,P2,C6);
  printf(" The Quartic equation Curve to Data : \n\n"
         "  s = %+.3f %+.3f*t %+.3f*t**2 %+.3f*t**3 %+.3f*t**4\n\n"
            ,x[R1][C1],x[R2][C1],x[R3][C1],x[R4][C1],x[R5][C1]);  
  
  stop();
  
  f_mR(A);
  f_mR(b);
  f_mR(Ab);
  f_mR(Q);
  f_mR(Q_T);
  f_mR(R);
  f_mR(invR);  
  f_mR(invR_Q_T); 
  f_mR(x); 
}
/* ------------------------------------ */
int main(void)
{
	
  fun();

  return 0;
}
/* ------------------------------------ */
/* ------------------------------------ */


Trouver la meilleur équation quartique qui s'ajuste au mieux aux points donnés.


On utilise la QR décomposition. Dans l'exemple suivant on utilise un autre algorithme sur le même exemple.



Exemple de sortie écran :
  -----------------------------------
 Fitting a quartic equation Curve to Data :

 A :
  +1.00   +1.00   +1.00   +1.00   +1.00 
  +1.00   +2.00   +4.00   +8.00  +16.00 
  +1.00   +3.00   +9.00  +27.00  +81.00 
  +1.00   +4.00  +16.00  +64.00 +256.00 
  +1.00   +5.00  +25.00 +125.00 +625.00 

 b :
  -5.00 
  +8.00 
  -7.00 
  +1.00 
  -4.00 

 Ab :
  +1.00   +1.00   +1.00   +1.00   +1.00   -5.00 
  +1.00   +2.00   +4.00   +8.00  +16.00   +8.00 
  +1.00   +3.00   +9.00  +27.00  +81.00   -7.00 
  +1.00   +4.00  +16.00  +64.00 +256.00   +1.00 
  +1.00   +5.00  +25.00 +125.00 +625.00   -4.00 

 Press return to continue. 


  -----------------------------------
 Q :
   +0.4472    -0.6325    +0.5345    -0.3162    +0.1195 
   +0.4472    -0.3162    -0.2673    +0.6325    -0.4781 
   +0.4472    +0.0000    -0.5345    +0.0000    +0.7171 
   +0.4472    +0.3162    -0.2673    -0.6325    -0.4781 
   +0.4472    +0.6325    +0.5345    +0.3162    +0.1195 

 R :
   +2.2361    +6.7082   +24.5967  +100.6231  +437.8221 
   +0.0000    +3.1623   +18.9737   +96.1332  +470.5469 
   +0.0000    +0.0000    +3.7417   +33.6749  +218.6197 
   +0.0000    +0.0000    +0.0000    +3.7947   +45.5368 
   -0.0000    -0.0000    -0.0000    -0.0000    +2.8685 

 Press return to continue. 


  -----------------------------------
 Q_T :
+4.4721e-01 +4.4721e-01 +4.4721e-01 +4.4721e-01 +4.4721e-01 
-6.3246e-01 -3.1623e-01 +0.0000e+00 +3.1623e-01 +6.3246e-01 
+5.3452e-01 -2.6726e-01 -5.3452e-01 -2.6726e-01 +5.3452e-01 
-3.1623e-01 +6.3246e-01 +0.0000e+00 -6.3246e-01 +3.1623e-01 
+1.1952e-01 -4.7809e-01 +7.1714e-01 -4.7809e-01 +1.1952e-01 

 invR :
+4.4721e-01 -9.4868e-01 +1.8708e+00 -4.4272e+00 +1.5060e+01 
+0.0000e+00 +3.1623e-01 -1.6036e+00 +6.2191e+00 -2.8387e+01 
-0.0000e+00 +0.0000e+00 +2.6726e-01 -2.3717e+00 +1.7281e+01 
+0.0000e+00 -0.0000e+00 +0.0000e+00 +2.6352e-01 -4.1833e+00 
-0.0000e+00 +0.0000e+00 -0.0000e+00 -0.0000e+00 +3.4861e-01 

 Press return to continue. 


  -----------------------------------
 Solving this system yields a unique
 least squares solution, namely   

 x = invR * Q_T * b :
   -184.00 
   +329.75 
   -191.87 
    +44.75 
     -3.63 

 The Quartic equation Curve to Data : 

  s = -184.000 +329.750*t -191.875*t**2 +44.750*t**3 -3.625*t**4

 Press return to continue.