Computer Programming Concepts and Visual Basic David I. Schneider

placed before the Scale method is executed.
9.3 BAR CHARTS
Drawing bar charts requires a variation of the line statement. If (x1, y1) and (x2, y2) are two
points on the screen, then the statement
picBox.Line (x1, y1) - (x2, y2), , B
draws a rectangle with the two points as opposite corners. If B is replaced by BF, a solid rectangle
will be drawn (see Figure 9-12).
FIGURE 9-12 Line Method with B and BF Options
EXAMPLE 1
The 1998 populations of California and New York are 32 and 18 million, respectively. Draw a bar chart
to compare the populations.
SOLUTION:
The following program produces the chart shown in Figure 9-13. The first five lines are the same as those
of a line chart with two pieces of data. The base of the rectangle for California is centered above the point
(1, 0) on the x axis and extends .3 unit to the left and right. (The number .3 was chosen arbitrarily; it had
to be less than .5 so that the rectangles would not touch.) Therefore, the upper-left corner of the rectangle
has coordinates (.7, 32) and the lower-right corner has coordinates (1.3, 0). Figure 9-14 shows the coordinates
of the principal points of the rectangles.
FIGURE 9-13 Bar Chart for Example 1
Private Sub cmdDisplayPop_Click()
‘Populations of California and New York
picPop.Scale (-1, 40)-(3, -5) ‘Specify coordinates
picPop.Line (-1, 0)-(3, 0) ‘ Draw x-axis
picPop.Line (0, -5)-(0, 40) ‘ Draw y-axis
picPop.Line (.7, 32)-(1.3, 0),,BF ‘Draw solid rectangle for CA
picPop.Line (1.7, 18)-(2.3, 0),,BF ‘Draw solid rectangle for NY
picPop.CurrentY = -1 ‘Vertical position of labels
Bar Charts 273