How to Make a Secondary Axis Graph in Numbers
By Richard Gaughan
The Numbers program in Apple's iWork office software suite gives you the option to plot your data in any one of more than a dozen basic chart formats. Options within those chart types give you even more possibilities. One option is the 2-axis chart, which lets you visualize variations in different parameters for the same items, such as students' performance on homework and on tests. The process is straightforward: select the 2-axis chart type, and then modify the format options until you get just what you're looking for.
Enter the label for your data in one column of the spreadsheet, and then enter the two series of related data in adjacent columns of the spreadsheet. For example, the first column could be students' names, and the next two columns could be their grades on math homework and math tests.
Highlight the label column and the two columns of data, select "Insert," hover over "Chart>," and then click "2-axis." The chart appears with both the primary and secondary axis values. The first data series defaults to a line plot and the second data series defaults to a column plot; the two are different colors.
Click on the chart, open the inspector window, and then click the "Chart" button to adjust display options for the title and legend options.
Click the "Axis" button -- with the chart still selected and the inspector window open -- to choose such characteristics as whether or not to show the axes, the number of values to be shown, and the location and spacing of tick marks.
Select the chart if it's not still selected, and then re-open the inspector window, if necessary. Click on one of the data displays on the chart to select one of the data series, then select the "Series" button to modify the labels and the data series type, and to swap the primary and secondary axes.
- If you put header labels in the table, they will automatically be used as data series markers, helping you keep track of which plot is from which column.
- You can choose separate axis styles for the primary and secondary axes, which means you can have a linear scale for one and a logarithmic scale for the other, if your data is more easily visualized in that format.
- Information in this article applies to Numbers '09. It may vary slightly or significantly with other versions.
First published in 1998, Richard Gaughan has contributed to publications such as "Photonics Spectra," "The Scientist" and other magazines. He is the author of "Accidental Genius: The World's Greatest By-Chance Discoveries." Gaughan holds a Bachelor of Science in physics from the University of Chicago.