public function f()
    {
        if(is_null($this->arr_f)){
            $arr = $this->frequency();
            array_walk(
                $arr, 
                function(&$v, $k, $n){
                    $v = $v / $n;
                }, 
                count($this)
            );

            $this->arr_f = $arr;
        }

        return $this->arr_f;
    }
public function f()
    {
        if(is_null($this->arr_f)){
            $arr = $this->frequency();
            array_walk(
                $arr, 
                function(&$v, $k, $n){
                    $v = $v / $n;
                }, 
                count($this)
            );

            $this->arr_f = $arr;
        }

        return $this->arr_f;
    }
public function f ( ) { if ( is_null ( $ this -> arr_f ) ) { $ arr = $ this -> frequency ( ) ; array_walk ( $ arr , function ( & $ v , $ k , $ n ) { $ v = $ v / $ n ; } , count ( $ this ) ) ; $ this -> arr_f = $ arr ; } return $ this -> arr_f ; }
Relative frequency, like frequency, but divide each but total amount.

@access public
@return array
Relative frequency like frequency but divide each but total amount .