Computer Programming Concepts and Visual Basic David I. Schneider

picOutput.Scale (-2, 12)-(12, -2) ‘Specify coordinate system
picOutput.Line (-2, 0)-(12, 0) ‘Draw x-axis
picOutput.Line (0, -2)-(0, 12) ‘Draw y-axis
picOutput.PSet (7, 6) ‘Draw center of circle
picOutput.Circle (7, 6), 3
End Sub
‘Draw the circle
[Run, and then click the command button. The contents of the picture box is shown in
Figure 9-5.]
FIGURE 9-5 Graph for Example 3
The numbers appearing in the Scale, Line, PSet, and Circle methods can be replaced by
variables or expressions. The following example demonstrates this feature.
EXAMPLE 4
Write an event procedure to draw a graph of the square root function.
SOLUTION:
We will graph the function for values of x from 0 to 100. See Figure 9.6.
Private Sub cmdDraw_Click()
Dim x As Single
‘Graph the Square Root Function
picOutput.Cls
picOutput.Scale (-20, 12)-(120, -2) ‘Specify coordinate system
picOutput.Line (-5, 0)-(100, 0) ‘Draw x-axis
picOutput.Line (0, -1)-(0, 10) ‘Draw y-axis
For x = 0 To 100 Step 0.2 ‘Plot about 500 points
picOutput.PSet (x, Sqr(x)) ‘Plot point on graph
Next x
End Sub
[Run, and then click the command button. The resulting picture box is shown in Figure 9-6.]
FIGURE 9-6 Graph of the Square Root Function
■ POSITIONING TEXT
Introduction to Graphics 263
There are times when text is placed on the screen in conjunction with graphics. This would be
the case if a graph were to be titled or a tick mark needed a label. The ability to position such