Microsoft Office Tutorials and References
In Depth Information
Data That Uses a Date or Time Scale
Practical Charting
Sales-03, Sales-04, and Sales-05 represent consecutive years, Excel is oblivious to
what these labels actually mean. You could chart a bunch of years that are far from
sequential (like Sales02, Sales04, and Sales08) and Excel would obediently (and
misleadingly) place each value on the category axis, spaced out evenly.
This snafu doesn’t present a problem in the previous example, but it’s an issue if you
need to chart years that aren’t spread out evenly. Fortunately, Excel offers an easy
solution. Instead of entering text labels, you can enter actual dates or times. Because
Excel stores dates and times as numbers, it can scale the chart accordingly (this
process is sometimes called category axis scaling ). Best of all, Excel automatically notices
when you’re using real dates, and kicks into action, making the appropriate
adjustments, as shown in Figure 19-11.
Figure 19-11:
The top chart
uses category axis
scaling to properly
space out dates,
even when values
are missing. The
bottom chart
doesn’t.
What’s happening in Figure 19-11 is worth examining in a bit of detail. The pictured
worksheet shows two charts that show the exact same data: a series of monthly sales
figures from two regions (covering the time period between January 2010 and
December 2011). The diamonds and triangles on the line charts indicate the data points
for which sales data is available. The twist is that a big chunk of data (the months
between August 2010 and June 2011) is missing. To make sure Excel handles this
omission correctly, you have to enter real date values (rather than text labels) for the
category axis. If you take that step, the chart Excel creates automatically uses a
continuous timescale, as shown in the top chart. (As you can see by looking at the data
points, no values fall in the middle of the series.)
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