mdcTwoInv.cxx

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/* Invert a symmetric 2x2 matrix.  Return 1 if inversion fails. */
 
int mdcTwoInv( double matrix[3], double invmat[3] ) {
 
  /* Declare variables. */
  double det, detinv;
 
  /**************************************************************************/
 
  det = matrix[0] * matrix[2] - matrix[1] * matrix[1];
  if ( det == 0.0 )
  {
    invmat[0] = 0.00001;
    invmat[2] = 0.00001;
    invmat[1] = 0.00000;
    return 1;
  }
  detinv = 1. / det;
 
  invmat[0] = matrix[2] * detinv;
  invmat[2] = matrix[0] * detinv;
  invmat[1] = -matrix[1] * detinv;
 
  return 0;
}