obs_vals->n_categories = 0;
obs_vals->n_allocated_categories = N_INITIAL_CATEGORIES;
obs_vals->vals = xnmalloc (N_INITIAL_CATEGORIES, sizeof *obs_vals->vals);
obs_vals->n_categories = 0;
obs_vals->n_allocated_categories = N_INITIAL_CATEGORIES;
obs_vals->vals = xnmalloc (N_INITIAL_CATEGORIES, sizeof *obs_vals->vals);