文中提到不能使用自定义公式的问题，我用引用Com控件的方法，但是速度比较慢

需要添加Microsoft.ScriptControl控件,公式只能使用JavaScript格式来写

 

using System;

using System.Collections.Generic; using System.Windows.Forms; using System.Drawing; namespace PlotFunctionForm { static class Program { sealed class PlotForm : Form { static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new PlotForm()); }  // 要画的函数，如果能在 TextBox 中输入函数的表达式就更好了  double Function(double x) { //使用Microsoft ScriptControl Com控件 MSScriptControl.ScriptControl sc = new MSScriptControl.ScriptControlClass(); sc.Language = "JavaScript"; string express = TextBox1.Text; express = express.Replace("x", x.ToString()); try {   double y = double.Parse(sc.Eval(express).ToString());    return y; } catch(Exception ex) { MessageBox.Show(ex.Message); return -1; } //double z = Math.Sin(x); //return z; // return Math.Sin(x); //double u = Math.PI - x; //double pi2 = Math.PI * Math.PI; //return 3 * x * x + Math.Log(u * u) / pi2 / pi2 + 1; } // 仅仅用来显示在屏幕上  string FunctionString() { return TextBox1.Text; //return "f(x) = 3 * x^2 + pi^-4 * ln[(pi-x)^2] + 1"; } const int yBase = 24; // 屏幕保留区域的高度  TextBox tbxX0, tbxX1; // 函数自变量的取值范围  TextBox TextBox1; Label label1=new Label(); Label label2=new Label(); PlotForm() { SuspendLayout(); Button btnSubmit = new Button(); btnSubmit.Text = "刷新"; btnSubmit.Location = new Point(0, 0); btnSubmit.Size = new Size(48, 24); btnSubmit.Click += new EventHandler(BtnSubmit_Click); label1.AutoSize = true; label1.Location = new System.Drawing.Point(55, 7); label1.Name = "label1"; label1.Size = new System.Drawing.Size(40, 12); label1.TabIndex = 0; label1.Text = "取值范围"; tbxX0 = new TextBox(); tbxX0.Text = "-3"; tbxX0.Location = new Point(110, 3); tbxX0.Size = new Size(50, 20); tbxX1 = new TextBox(); tbxX1.Text = "3"; tbxX1.Location = new Point(165, 3); tbxX1.Size = new Size(50, 20); label2.Text = "公式"; label2.Location = new Point(220, 7); label2.Size = new Size(30, 20); TextBox1 = new TextBox(); TextBox1.Text = "Math.sin(x)"; TextBox1.Location = new Point(255, 3); TextBox1.Size = new Size(200, 20); Controls.AddRange(new Control[] { btnSubmit, tbxX0, tbxX1, TextBox1,label1,label2 }); Text = "Plot"; BackColor = Color.White; ClientSize = new Size(600, 600 + yBase); // WindowState = FormWindowState.Maximized;  ResumeLayout(false); } void BtnSubmit_Click(object sender, EventArgs e) { Invalidate(); } protected override void OnSizeChanged(EventArgs e) { Invalidate(); base.OnSizeChanged(e); } protected override void OnPaint(PaintEventArgs e) { double x0 = double.Parse(tbxX0.Text); double x1 = double.Parse(tbxX1.Text); Graphics gc = e.Graphics; Size size = ClientSize; int i0 = 0; int i1 = size.Width - 1; int j0 = yBase; int j1 = size.Height - 1; Pen pen = new Pen(Color.Black, 1); gc.DrawLine(pen, i0, j0, i1, j0); // 画图区和保留区的分界线  double rx = (x1 - x0) / (i1 - i0); double y0=0, y1=1; GetFunctionValueRange(x0, rx, i0, i1, out y0, out y1); double ry = (y1 - y0) / (j1 - j0); Out(gc, 0, "ClientSize: {0}x{1}", i1 - i0 + 1, j1 - j0 + 1); Out(gc, 1, FunctionString()); Out(gc, 2, "x:[{0}, {1}] range:{2}", x0, x1, x1 - x0); Out(gc, 3, "y:[{0}, {1}] range:{2}", y0, y1, y1 - y0); Out(gc, 4, "rx:{0}", 1 / rx); // 函数自变量每单位值用多少个象素表示  Out(gc, 5, "ry:{0}", 1 / ry); // 函数的值每单位值用多少个象素表示  Out(gc, 6, "r :{0}", rx / ry); // 该值如果小于1表示图形纵向被压扁，反之则被拉伸  pen.Color = Color.Green; int j = j1 + (int)(y0 / ry); if (j >= j0 && j <= j1) gc.DrawLine(pen, i0, j, i1, j); // x坐标轴  int i = i0 - (int)(x0 / rx); if (i >= i0 && i <= i1) gc.DrawLine(pen, i, j0, i, j1); // y坐标轴  pen.Color = Color.Red; for (i = i0; i <= i1; i++) { double x = x0 + (i - i0) * rx; double y = Function(x); if (double.IsInfinity(y) || double.IsNaN(y)) continue; j = j1 - (int)((y - y0) / ry); if (j > j1 || j < j0) continue; gc.DrawLine(pen, i, j, i + 1, j); // 画函数的图形  } base.OnPaint(e); } // 函数值的取值范围  void GetFunctionValueRange(double x0, double rx, int i0, int i1, out double y0, out double y1) { y0 = double.MaxValue; y1 = double.MinValue; for (int i = i0; i <= i1; i++) { double x = x0 + (i - i0) * rx; double y = Function(x); if (double.IsInfinity(y) || double.IsNaN(y)) continue; if (y0 > y) y0 = y; if (y1 < y) y1 = y; } } // 在指定的位置写字符串  void Out(Graphics gc, int line, string fmt, params object[] args) { gc.DrawString(string.Format(fmt, args), new Font("Courier New", 10), Brushes.Blue, new PointF(5, yBase + 15 * line)); } } } }

本文转自tiasys博客园博客，原文链接：http://www.cnblogs.com/tiasys/archive/2010/03/24/1693638.html，如需转载请自行联系原作者