绘制 sigmoid函数
2013年08月30日
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//用来计算从-4到4之间的sigmoid函数值的静态函数
public class Uitility
...{
public static PointF[] GetPoints()
...{
PointF[] mypos=new PointF[400];
int j=0;
for(double i=-4;i<=4;i+=0.02)
...{
mypos[j]= new PointF((float)i,(float)Sigmoid(i));
j++;
}
return mypos;
}
public static double Sigmoid(double x)
...{
return 1/(1+Math.Pow(Math.E,-x));
}
}
//调用函数,完成函数的picturebox1上的绘制
Graphics grfx=pictureBox1.CreateGraphics();
int picwidth=pictureBox1.Width;
int picheight=pictureBox1.Height;
float midx=(float)picwidth/2;
float midy=(float)picheight/2;
Pen bb=new Pen(Brushes.Black,2);
grfx.DrawLine(Pens.Red,new Point(0,picheight-1),new Point(picwidth,picheight-1));//横坐标
grfx.DrawLine(Pens.Red,new Point((int)midx,picheight),new Point((int)midx,0));
PointF[] cc=Uitility.GetPoints();
PointF[] realone=new PointF[cc.Length];
int cclen=cc.Length;
//将与坐标无关的数值转换成与坐标相关的点
for(int i=0;i<cclen;i++)
...{
float fx=cc[i].X*picwidth/8+midx;
float fy=cc[i].Y*picheight;
realone[i]=new PointF(fx,-fy+picheight);
}
grfx.DrawLines(bb,realone);