Computer Programming Concepts and Visual Basic David I. Schneider

‘space of 1.75 radii will remain on right for legends.
leftEdge = -1.25 * radius
rightEdge = 2.75 * radius
‘Force vertical scale to match horizontal scale; ‘center origin vertically
topEdge = 2 * radius * (picShare.Height / picShare.Width)
bottomEdge = -topEdge
picShare.Cls
picShare.Scale (leftEdge, topEdge)-(rightEdge, bottomEdge)
circumf = 2 * 3.14159
ReDim cumPercent(0 To numItems) As Single
cumPercent(0) = .0000001 ‘a value of “zero” that can be made negative
For i = 1
To numItems cumPercent(i) = cumPercent(i - 1) + quantity(i)
startAngle = cumPercent(i - 1) * circumf
stopAngle = cumPercent(i) * circumf
picShare.FillStyle = (8 - i) ‘use fill patterns 7, 6, and 5
picShare.Circle (0, 0), radius, , -startAngle, -stopAngle
Next i
End Sub
Private Sub Locate (x As Single, y As Single)
picShare.CurrentX = x
picShare.CurrentY = y
End Sub
Private Sub ReadData(category() As String, quantity() As Single, _ numItems As
Integer)
Dim i As Integer ‘Load categories and percentages of market share
‘Assume the data have been placed in the file BROWSERS.TXT
‘(First line in file is “Internet Explorer”, .44)
Open “BROWSERS.TXT” For Input As #1
For i = 1 To numItems
Input #1, category(i), quantity(i)
Next i
Close #1
End Sub
Private Sub ShowLegend(category() As String, numItems As Integer, _ radius As
Single)
Dim lblHght As Single, legendSize As Single
Dim i As Integer, vertPos As Single
‘Place legend centered to right of pie chart
‘Make separation between items equal to one line of text
‘“Text lines” needed for legends is thus (2*numItems-1)
lblHght = picShare.TextHeight(“ ”)
legendSize = lblHght * (2 * numItems - 1)
For i = 1 To numItems
picShare.FillStyle = (8 - i)
vertPos = (legendSize / 2) - (3 - i) * (2 * lblHght)
picShare.Line (1.1 * radius, vertPos)-(1.4 * radius, _ vertPos +
lblHght), ,B
Call Locate(1.5 * radius, vertPos)
picShare.Print category(i)
Next i
End Sub
Pie Charts 281