WFA_psychometric_chart.Form1_main.plot_by_DBT_Enthalpy C# (CSharp) Method

        public int plot_by_DBT_Enthalpy(double dbt, double enthalpy)
        {
            //this is DBT 
            double x_axis = dbt;
            double h = enthalpy;
            // MessageBox.Show("h = " + h+" T = "+dbt);

            //lets fit this value in the curve...
            double x1 = (h - 12.5) / 3.5;
            //        MessageBox.Show("X1= " + x1);
            double y1 = x1 + 5;//this is given temp..
            //      MessageBox.Show("y1= " + y1);
            double x2 = h;
            double y2 = 0;

            //MessageBox.Show("x2= " + x2+" y2  = "+y2);

            double x = dbt;
            double y = y1 + (((y2 - y1) * (x - x1) / (x2 - x1)));

            double y_axis = y;

            //MessageBox.Show("y = " + y);

            chart1.Series.Add("SeriesDBT_enthalpy" + index);//this is already delceared in chart control so we dont need it
            chart1.Series["SeriesDBT_enthalpy" + index].ChartType = SeriesChartType.Point;
            chart1.Series["SeriesDBT_enthalpy" + index].Color = Color.Blue;
            chart1.Series["SeriesDBT_enthalpy" + index].MarkerSize = 15;
            chart1.Series["SeriesDBT_enthalpy" + index].Label = "DBT = " + dbt + "degC ,enthalpy = " + enthalpy;
            //chart1.Series["SeriesDBT_HR" + index].;
            chart1.Series["SeriesDBT_enthalpy" + index].Points.AddXY(x_axis, y_axis);

            index++;



            return 0;
        }