# Optsee® Project Portfolio Management Bubble Charts

Bubble charts or bubble graphs are extremely useful in project portfolio management for comparing the relationships between projects in 3 data dimensions: the horizontal (X-axis) data, the vertical (Y-axis) data, and the data represented by the bubble size. 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 the circle or “bubble” centered around the XY point.

Bubble charts can be used in project portfolio management to visualize the relationships between projects in dimensions such as cost, value, and risk. 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.

In the Figure 1 example, the bubble chart area is bounded by the highest and lowest Project attribute values and divided into quadrants (X-axis and Y-axis in center of the chart). This allows you to identify the most attractive and least attractive areas. In this chart, the most attractive area is the upper left quadrant (higher SMART Scores and low cost) versus the least attractive lower right quadrant (lower SMART Scores and higher costs).

In this chart, the “best” projects are the ones with the largest “Profit” bubbles in the upper left quadrant, and the “worst” project (lowest overall value) are in the lower right quadrant.

## 3-Dimensional Bubble Charts

Three-dimensional (or "3D") Bubble charts (or bubble graphs) compare the relationships between projects in 4 data dimensions: a horizontal X-axis, a horizontal Y-axis, a vertical Z-axis, and the bubble size. 3D bubble charts are extremely useful in project portfolio management and business investment decisions when you want to compare cost, risk, reward, and resource data simultaneously in a single chart, as illustrated in the example below.

3D Bubble Chart Figure 1: This chart shows the the relationship between “Costs” (X-Axis), “Resources” (Y-Axis), Probability of Success (vertical or Z-axis) and “Profit” (Bubble Size). The most desirable quadrant for projects would be in the upper left rear quadrant (lower costs, lower resource requirements, and higher probability of success)

Because 3D Bubble charts represent 3 dimensional space on a flat surface it can be difficult to see all the bubbles in the chart space. In Optsee® you can explore the data space by rotating the chart using the buttons at the bottom of the form. This lets you explore the data in a very natural manner. The charts rotate around the axes extending orthogonally from the X-Y and Y-Z planes as illustrated in Figure 2.

**3D Bubble Chart Figure 2: This illustrates the axes of rotation for a 3D bubble chart.**

**3D Bubble Chart Rotation Video (silent, 11 seconds): This video shows the full rotation of a Optsee® 3D bubble chart**

The chart in the video above uses "drop-lines" to help locate the bubbles in the chart space. Drop-lines are two lines that run from the center of each bubble to the chart grids. One line goes to a vertical grid and one goes to the horizontal grid. These drop-lines let you quickly locate the center of the bubble relative to the XY, XZ, or YZ graphs. You can also toggle the drop-line display on and off. Example 2 shows the same chart from Example 1 with drop-lines turned on.