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
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
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.
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.