In Bubble Chart Pro, one can choose between “Bubbles proportional to area” or “Bubbles proportional to radius,” and the selected relationship is stated on the resulting bubble chart.īubbles are usually differentiated by color, pattern, number or name labels, or a combination of these. However, it should be specified on the chart as to what representation is being made.

For example, if the bubble data is similar in magnitude and you want more easily contrast the bubbles. This isn’t to say that one should never use the radius to represent the data as it can be useful if one wants to exaggerate the differences between the data objects or projects. Notice how the bubble sizes compare to Example 1. For a proportionally accurate representation of the data, bubble data should be represented directly by the area using the circumference of the circle, which grows the bubble area linearly in relationship to the diameter (circumference=π*diameter).īubble Chart Example 3: The same as Bubble Chart Example 1, but the bubble size has been changed to be proportional to the radius. If the data is proportional to the bubble radius, the data will be skewed because bubble area grows exponentially as the square of the radius (Area=π*r^2). Bubbles with larger areas have higher probabilities of success.Īs you can see, studying a project portfolio in several bubble charts using different dimensions of business relationships can be a great help in making insightful business investment decisions.īubble charts can be misleading if care isn’t taken to understand the relationship between bubble size and the data the size represents. In the bubble chart examples above, the most desirable quadrant is in the upper left (higher profit and lower cost) and the least desirable quadrant is the lower right (high cost and lower profits). By visualizing project portfolios using bubble charts, you can find clusters of relatively attractive projects in one area of the graph, such as areas of high value, low cost, and/or low risk, and compare them with relatively less attractive projects in a different area of the graph, such as an area of low value, high cost, and/or high risk. Essentially, bubble charts are like XY scatter graphs except that each point on the scatter graph has an additional data value associated with it that is represented by the size of a circle or “bubble” centered around the XY point.īubble Chart Example 1: This chart shows the relationship between “Probability of Success (%)” (Y-Axis), “Cost” (X-Axis), and “Profit” (Bubble Size).īubble Chart Example 2: The same as Example 1, but the bubble size variable has been removed so now it is displayed as a scatter chart.īubble charts are often used in business to visualize the relationships between projects or investment alternatives in dimensions such as cost, value, and risk. What Are Bubble Charts and How Are They Used? See also 'How to Make a Bubble Chart' by clicking here.įor background on 3-dimensional (3D) bubble charts, see 'What are 3D Bubble Charts' by clicking here.įor background on Packed Bubble charts, see 'What are Packed Bubble Charts' by clicking here.īubble charts or bubble graphs are extremely useful graphs for comparing the relationships between data objects in 3 numeric-data dimensions: the X-axis data, the Y-axis data, and data represented by the bubble size.