#include "polifitgsl.h"

bool polynomialfit(int obs, int degree,
		   double *dx, double *dy, double *store) /* n, p */
{
  gsl_multifit_linear_workspace *ws;
  gsl_matrix *cov, *X;
  gsl_vector *y, *c;
  double chisq;

  int i, j;

  X = gsl_matrix_alloc(obs, degree);
  y = gsl_vector_alloc(obs);
  c = gsl_vector_alloc(degree);
  cov = gsl_matrix_alloc(degree, degree);

  for(i=0; i < obs; i++) {
    for(j=0; j < degree; j++) {
      gsl_matrix_set(X, i, j, pow(dx[i], j));
    }
    gsl_vector_set(y, i, dy[i]);
  }

  ws = gsl_multifit_linear_alloc(obs, degree);
  gsl_multifit_linear(X, y, c, cov, &chisq, ws);

  /* store result ... */
  for(i=0; i < degree; i++)
  {
    store[i] = gsl_vector_get(c, i);
  }

  gsl_multifit_linear_free(ws);
  gsl_matrix_free(X);
  gsl_matrix_free(cov);
  gsl_vector_free(y);
  gsl_vector_free(c);
  return true; /* we do not "analyse" the result (cov matrix mainly)
		  to know if the fit is "good" */
}