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Thursday, October 15, 2009

Bubble Chart Tips

I will never forget while as a business analyst working directly with Senior Leadership, I was shown a funny looking graphical chart that took up half a page of a USA Today business page and was asked to replicate for the business function I was working for. As an analyst I already had the innate ability to look at charts, tables, etc. and decipher their meaning for the business to take action. This bubble chart stumped me. It took me an hour to figure what the chart meant and then another day to replicate it for this senior leader in Excel, only to find out after bringing to him that he wanted the measures on completely different axis then what was presented. This is when I fell in love with database analytics tools like OBIEE. OBIEE takes a simplistic approach in creating a bubble chart while giving you flexibility to make it dynamic for your end user.

A typical line or bar chart has two axis’s: x (the bottom axis of the chart) and y (the left axis of the chart). The bubble chart has a 3rd axis called the z-axis, which highlights the most meaningful piece of data that your viewer is visually searching for. Below are 3 examples using Sales Units, Sales Dollars and Price per Unit to view in a bubble chart within OBIEE.

Example 1: The following chart places the Price per Unit in the z-axis. Notice how the sizes of the bubbles are approximately the same size. This chart shows that each region is selling the product around the same price per unit, however, the Eastern Region is selling at a higher volume therefore having higher sales. The Eastern Region is noticeable as an outlier because of its placement within the chart. Configuring the Bubble Chart with little to no disparity of the z-axis value doesn’t draw attention to the size of the bubbles, visually this may not be a proper use of a Bubble Chart. A scatter chart may be better suited for this type of configuration.

Example 2: The following chart places Units in the z-axis. With the Price per Unit on the y-axis you can see how the price per unit of the products have smaller range (this is why the bubbles were close to the same size above). This particular bubble chart actually shows that the Eastern Region has a higher volume than the other region based off of the size of the bubble.

But what if you wanted to view the chart using your company’s three key measures for the region in the format specific to your needs?

Example 3: By utilizing the column selector feature in OBIEE, you can create a dynamic view of how you want the placement of your businesses key metrics within the bubble chart. Remember to uncheck the ‘Automatically refresh when a new column is selected’ so that the chart does not change while selecting the measures for the proper axis.