The Case FOR Dual-Axis Charts in Power BI
The ultimate goal of many reports is to help someone make a decision.
The ultimate goal of many reports is to help someone make a decision. That could be something as minor as choosing what product to produce, or more important, like determining the future course of your company. In that sense, the information needs to be concise; more importantly, it needs to be clear.
An easy way to get that information across is in a graphical representation (a fancy term for a chart). With Microsoft’s Power BI, you can easily take all kinds of data and create many different types of charts and display them in an easy-to-understand report to tell a story about it. One quick and easy way to do this is by using a dual-axis chart.
For those of you who haven’t fainted from that blasphemous statement, let me explain why I believe dual-axis charts can be incredibly useful.
First of all, let’s answer the most obvious question: What is a dual-axis chart? Simply put, a dual-axis chart (often times referred to as a combo chart) incorporates 2 vertical axes. In a typical column chart, the main values are placed on the left side of the chart, or the y-axis. A dual-axis chart places another set of values along the right side of the chart (or z-axis).And while the y-axis is most often represented in columnar format, the information on the z-axis can be shown with a line; hence, it’s a combination of two charts.
Once again, I can hear the complaints from here:
- That makes it too cluttered and hard to read!
- Too much information on one chart makes it more confusing!
- Too much color and too many shapes will make my boss’s eyes hurts (ok, I made up that last one)
Let me give you an example.
As a training manager, I need to keep track of instructors’ average scores every month.
This is easy enough to do, once the information is properly calculated, especially in Power BI. I create a measure that adds the scores together and divide them by the number of evaluations they received for a class.
All scores are then combined and divided by the total evaluations for the month, to get an average score. That measure can then be placed in the y-axis of a chart, like this:
Because it’s an integral part of that calculation, I also need to make sure I know how many evaluations per month each instructor has. If I put that into a chart, it looks like this:
By creating two separate charts, I have to bounce back and forth to see whether the instructor had a good month, or if they possibly had one person who gave him/her a bad score, thereby tanking their score for the month. But by combining them into one chart, I can see both with ease:
Let’s face it: bosses like pretty pictures. Power BI makes it really easy to create easy-to-read and easy-to-understand reports like this with just a few clicks. Give it a try, or try your own system, to create charts and help your company steer its future.