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.