Updated: Feb 20, 2022
Have you ever had to plot two series of data, one in % rate and the other in US$ Millions in one chart, and the combination of the two in one chart creates a confusing presentation as the primary and secondary axis do not align? There is a very simple way to align the 0 line of primary and secondary axis, so the display is improved. The solution is to ensure the ratio of Maximum and Minimum bounds of each Y axis (primary and secondary) is set equal. Let’s see this in an example.
In the example in the video, net debt deciles of all public equities (public companies in North America) are plotted as a line chart and year to date (“YTD”) returns of the all companies in each decile as of three different dates of April 24, May 26 and June 26 is plotted on the secondary axis as a clustered column chart. As noticed, YTD returns are in % term and Net Debt balances in USD Millions and the scale and span of these time series do not match. Hence the first shot at plotting the data confuses the readers as the 0 line of the two primary and secondary are not aligned properly.
In the second try, the ratio of Maximum Bound and Minimum Bound of the two axis’s (under Axis Options) are matched; however, since the range of the data series are quite different, the stacked column chart look quite small.
In the third try, we set the ratio of Maximum Bound/Minimum Bound of the two axis’s to -50%. This allows for the selection of the appropriate upper and lower bound and both charts, the line as well as the stacked column chart look proportional and the zero line of both axis’s are matched.