forum, admin rank, need help

[eluser]benfike[/eluser]
Hi! I have an forum, php beast from this page. And i wanted change admin ranks...
My site have 3 rank.
rank 0= user
rank 1= only news writer (admin)
rank 2= full admin rank

and here the forum , user class file:

function is_admin($id = '')
{
$this->CI->db->where('id', $id);
$this->CI->db->select('rank');
$query = $this->CI->db->get('users');
if($query->num_rows > 0)
{
$rank = $query->row();
return $rank->rank;
}

return false;
}

and i wanted to change this, where rank=0 not admin and where rank 1 or 2 Admin.

Help me pls