Computer Programming Concepts and Visual Basic David I. Schneider

270 Computer Programming Concepts and Visual Basic
FIGURE 9-10 Line Patterns
Styling is useful when displaying several line charts on the same coordinate system.
EXAMPLE 2
Alter the program in Example 1 so that it will draw line charts displaying the male, female, and total
enrollments of 2-year colleges.
SOLUTION:
The data file must be changed to contain the enrollment figures for males and females, and arrays must
be created to hold this information. The totals can be computed from the other numbers. The styled lines
for male and female enrollments must be drawn. Finally, legends must be given to identify the different
line charts. Figure 9-11 shows the picture box that results from the modified program.
‘In (Declarations) section of (General)
Dim numYears As Integer, maxEnroll As Single
Private Sub cmdDraw_Click()
‘Line Charts of Two-Year College Enrollments
numYears = 5
ReDim label(1 To numYears) As String
ReDim male(1 To numYears) As Single
ReDim female(1 To numYears) As Single
ReDim total(1 To numYears) As Single
Call ReadData(label(),male(),female(),total())
Call DrawAxes
Call DrawData(male(), female(), total())
Call ShowTitle
Call ShowLabels(label())
Call ShowLegend
End Sub
Private Sub DrawAxes()
‘Draw axes
picEnroll.Scale (-1, 1.2 * maxEnroll) - (numYears + 1, -.2 * maxEnroll)
picEnroll.Line (-1, 0)-(numYears + 1, 0)
picEnroll.Line (0, -.1 * maxEnroll)-(0, 1.1 * maxEnroll)
End Sub
Private Sub DrawData(male() As Single, female() As Single, total() As Single)
Dim i As Integer
For i = 1 To numYears
If i < numYears Then
‘Draw lines connecting data points
picEnroll.DrawStyle = 2
picEnroll.Line (i, male(i))-(i + 1, male(i + 1))
picEnroll.DrawStyle = 1