Re: [Help-gsl] Help

[Joakim Hove]

"Kaustubh Patil" <address@hidden> writes:

> Dear Sir/Madam, 
> I am using GSL for vector and matrix
> manipulations. I need a function that can give a (symmetrical)
> matrix formed by (v * v^T). 

This *quick and naive* hack works at least:

void vector_mul_transpose(const gsl_vector *v, gsl_matrix *m) {
  size_t i,j;

  if (v->size != m->size1 || m->size1 != m->size2) {
    fprintf(stderr,"Dimensions do not agree *aborting* \n");
    exit(1); 
  }

  for (i=0; i < v->size; i++) {
    double vi = gsl_vector_get(v,i);
    for (j=i; j < v->size; j++)
      gsl_matrix_set(m,i,j,vi * gsl_vector_get(v,j));
  }

  /* 
     Filling in the lower part of the symmetric matrix.
  */

  for (i=0; i < v->size; i++) 
    for (j=0; j < i; j++)
      gsl_matrix_set(m,i,j,gsl_matrix_get(m,j,i));
}



-- 
Joakim Hove
hove AT ift uib no
+47 (55 5)8 27 90
http://www.ift.uib.no/~hove/