Microsoft Office Tutorials and References

In Depth Information

**Working with Chart Axes**

Two of Excel’s chart types are different from the other chart types in one important respect. Scatter

charts and bubble charts use
two
value axes. For these chart types, both axes represent numeric

scales.

Figure 7-17 shows two charts (a scatter chart and a line chart) that use the same data. The data shows

world population estimates for various years. Note that the interval between the years in column A is

not consistent.

Figure 7-17:
These charts plot the same data but present very different pictures.

The scatter chart, which uses two value axes, plots the years as numeric values. The line chart, on the

other hand, uses a (non-numeric) category axis, and it assumes that the categories (the years) are

equally spaced. This, of course, is not a valid assumption, and the line chart presents a very

inaccurate picture of the population growth: It appears to be linear, but it’s definitely not.

For more information about time-based axes, refer to the “Using time-scale axes”

section later in this chapter.

Cross-Ref

Value axis scales

The numerical range of a value axis represents the axis’s scale. By default, Excel automatically scales

each value axis. It determines the minimum and maximum scale values for the axis, based on the

numeric range of the data. Excel also automatically calculates a major unit and a minor unit for each

axis scale. These settings determine how many intervals (or tick marks) are displayed on the axis and

determine how many gridlines are displayed. In addition, the value at which the axis crosses the

category axis is also calculated automatically.