Here's a link to my blog post, which responds to a comment directly from David, about his essay "Why Johnny Can't Code."
http://theschwartz.wordpress.com/2006/09/26/david-brin-proves-blogs-work/
The attached zip file (see link above) has the Phrogram code for this example.
Here a screenshot:
And here's the code, pasted:
Program PlotCosineFunction
Method Main()
Define X As Decimal = -300.0
Define Y As Decimal = 0.0
Define myPen As Pen
SetAlgebraCoordinates()
// Draw the axes
myPen.LineWidth = 3
myPen.Color = Colors.Black
myPen.MoveTo(-300, 0)
myPen.DrawTo(300, 0)
myPen.MoveTo(0,-300)
myPen.DrawTo(0, 300)
// draw the function
myPen.Color = Blue
Define LastX As Decimal
Define LastY As Decimal
While X < 300
LastX = X
LastY = Y
// Divide and multiply by 40 in order to exagerate the
// function so it's pattern is visible using pixel
// coordinates. You can see different functions plotted
// by commenting one out and uncommenting another
Y = Cos(X / 40) * 40 // Cosine function
//Y = Sin(X / 40) * 40 // Sine function
//Y = Tan(X / 40) * 40 // Tangent function
//Y = ArcTan(X / 40) * 40 // ArcTangent function
//Y = ((X/40) * (X/40)) * 40 // X squared is a parabola
X = X + 3
// Don't draw the line when calculating the very first point
If LastX > -300 Then
myPen.DrawTo( X, Y )
Else
myPen.MoveTo( X, Y )
End If
End While
End Method
End Program
This could of course be a fancier example, but in the interests of blogging an example I wanted to keep it as simple as possible.