数值分析（php实现)一：Lagrange插值(2)

              }

              return $L;

    }

    public function draw(){

        $img = imagecreate(500,500);

        imagecolorallocate($img,255,255,2);

        $num = count($this->dot['x']);

        $max = 0;

        for($i = 0;$i < $num;$i++) $max = $max < $this->dot['x'][$i] ? $this->dot['x'][$i]:$max;

        $r = 7;//点的半径

        $step = 0.1;//步长

        for($i = 0;$i < $num;$i++){

            imagefilledellipse($img,$this->dot['x'][$i],$this->dot['y'][$i],$r,$r,1);

        }

        for($i = $this->dot['x'][0]-10;$i < $max + 10;$i += $step){

            $current_x = $i;

            $current_y = $this->get_y($current_x);

            $next_x = $i + $step;

            $next_y = $this->get_y($next_x);

            imageline($img,$current_x,$current_y,$next_x,$next_y,1);

        }

        header("Content-type: image/png");

        imagepng($img);

        imagedestroy($img);

    }

}

$x = new Lagrange(array('x'=>array(10,30,100,120,220),'y'=>array(20,40,240,220,340)));

$x->draw();

?>

摘自 pcenshao