public void Point_databind(PointList pl)
        {
            chart1.Series.Clear();      //清空图表

            Series s1 = new Series();   //添加一条曲线
            s1.Points.DataBind(pl.list, "x", "y", "");   //数据绑定

            s1.ChartType = SeriesChartType.Point;   //曲线类型为点
            chart1.Series.Add(s1);      //将曲线添加到图表
        }


        public void Start(PointList pl, double a)
        {
            chart1.Series.Clear();   

            num = 0;
            for (int i = 0; i < pl.count; i++)
            {
                pl.list[i].Is_z = false;
                pl.list[i].l = 0;
            }
            mmsa(pl, a);

            Series s1 = new Series();
            for (int i = 0; i < pl.count; i++)
            {
                DataPoint dp = new DataPoint();     //添加一个点
                dp.XValue = pl.list[i].x;           //给横坐标赋值
                dp.SetValueY(pl.list[i].y);         //纵坐标赋值
                if (pl.list[i].Is_z)
                {
                    dp.MarkerSize = 20;             //点的大小
                    dp.MarkerStyle = MarkerStyle.Star5;   //点类型
                }

                dp.MarkerColor = color[(pl.list[i].l)];
                s1.Points.Add(dp);
            }

            s1.ChartType = SeriesChartType.Point;
            chart1.Series.Add(s1);            
        }