Comments on: Secondary Axes that Work – Proportional Scales

By: Steve

Steve — Sun, 29 Apr 2012 03:06:47 +0000

Hi Jon

Thanks for a very helpful article.

I thought readers might be interested that there is an unseen catch when adding a secondary y-axis to a chart, at least in Excel 2010. I created a chart following your instrutions showing distortion in four amplifiers. Three data series were linked to the LHS y-axis showing distortion as a percentage. This axis has a log scaling. One data series was linked to the RHS y-axis showing distortion in dB. The two axes were aligned by manually setting their max and min values.

The chart looked fine until I tried to reformat the x-axis (frequency) with log scaling. The three data series linked to the left y-axis rescaled correctly but not the series linked to the right y-axis.

After much searching and heartache, I found that Excel linked the single data series not only to the RHS y-axis, but also to a secondary x-axis. This secondary x-axis was not visible and consequently did not show up in the list of chart elements available for reformatting.

The solution (Excel 2010) is to make the secondary x-axis visible. To do this, click on the chart and go to Chart Tools/Layout/Axes/Secondary Horizontal Axis/Show Default Axis. The secondary x-axis can now be selected and reformatted so that it is identical to the primary axis. It can then be made invisible again from Chart Tools/Layout/Axes/Secondary Horizontal Axis/None.

In a nutshell: if you make a chart with two vertical axes and find that reformatting the horizontal axis does not work for all data series plotted, look for a hidden horizontal axis and make it visible, reformat it as necessary, then make it invisble again.

I hope this prevents someone getting as frustrated as I got. Sometimes one does feel that Excel is very good at applying single-click fancy effects on a chart, effects that I don’t want, yet obscures basic adjustments that should be instantly and intuitively available.

By: Jon Peltier

Jon Peltier — Wed, 15 Feb 2012 13:18:59 +0000

Stoyan -

It is possible to add a secondary horizontal axis the same way that you add a secondary vertical axis. And a secondary horizontal axis is as prone to comprehension issues as is a secondary vertical axis.

By: Stoyan Karakashev

Stoyan Karakashev — Wed, 15 Feb 2012 11:46:25 +0000

I need to know if it is possible to make a secondary X axis. Everyone knows 2 secondary axes are possible – horizontal and vertical. How to make horizontal one?

By: Nash Jaikharan

Nash Jaikharan — Fri, 27 Jan 2012 08:08:54 +0000

I found great value in the use of incorporating secondary graphs. In certain cases, inclusion of a secondary graph (axis) completes the story that needs to be told.

Much appreciated. I have certainly learnt something new.

By: Jon Peltier

Jon Peltier — Fri, 13 Jan 2012 17:53:55 +0000

Tom -

I am not hesitant to use primary and secondary axes for an audience that has a strong scientific or engineering background, which obviously includes yourself.

By: Tom M

Tom M — Fri, 13 Jan 2012 16:31:24 +0000

Secondary axis plots that were easier to do with the older version of excel can be very useful when you are plotting things like reactions that have peak times and temperatures that sometimes work in an orderly inverse relationship but when specific variables are induced do not. The best plot for these is a bar/line graph where the two variables are clearly defined. It is also useful when doing Pareto analysis to use the bars for the individual counts and a line that will easily delineate the 80% or 90% cumulative area to clearly concentrate where your focus should be.