Computer Programming Concepts and Visual Basic David I. Schneider

280 Computer Programming Concepts and Visual Basic
The FillStyle and FillColor properties can be used when creating rectangles. The statements
picBox.FillStyle = s=
picBox.Fill Color = vbColor
pic Box.Line (x1, y1) - (x2, y2), , 8
draw a rectangle filled with the pattern specified by s in the color specified by vbColor. This
capability is often used when creating the legend to accompany a graph.
The procedure for drawing a pie chart is as follows:
1. Read the categories and the quantities into arrays, such as category() and
quantity().
2. Determine the radius lines. The number associated with the ith radius line is
cumPercent(i). This number is a total of quantity(i) and the preceding
percentages.
3. Draw and fill each sector with a pattern. The first sector extends from the horizontal
radius line to radius line 1, the second sector from radius line 1 to radius
line 2, and so on.
4. Draw rectangular legends to associate each sector with its category.
EXAMPLE 5
Table 9.2 gives the market share of Internet browsers for July 1998. Construct a pie chart that displays the
market share.
TABLE 9.2
Browser Market Share, July 1998
Percent of Total Market
Internet Explorer 44
Netscape Navigator 42
Other 14
SOLUTION:
Figure 9-23 shows the output displayed by the following program.
Private Sub cmdDraw_Click()
Dim numItems As Integer, radius As Single
‘Draw pie chart of Browser Market Share
numItems = 3
ReDim category(1 To numItems) As String
ReDim quantity(1 To numItems) As Single
Call ReadData(category(), quantity(), numItems)
Call DrawData(quantity(), numItems, radius)
Call ShowLegend(category(), numItems, radius)
Call ShowTitle(radius)
End Sub
Private Sub DrawData(quantity() As Single, numItems As Integer, _ radius As
Single)
Dim circumf As Single, leftEdge As Single, rightEdge As Single
Dim topEdge As Single, bottomEdge As Single, i As Integer
Dim startAngle As Single, stopAngle As Single
‘Draw and fill each sector of pie chart
‘All scaling and text positioning done as a percentage of radius radius = 1
‘actual value used is not important
‘Make picture 4 radii wide to provide plenty of space for
‘circle and legends. Place origin 1.25 radii from left edge;