Graph ► Support ► Bubble Graph
A bubble graph adds a separate dimension to a Set Of 2D Points task in the following way. The Set Of 2D Points task can show "curves" and also mark the location of a 2D point with a circle (which is called a marker). When the curves are displayed, the graph is called a "line graph". When only the markers are displayed, the graph is called a "scatter graph". The circle marks the location of a data point on the two coordinates displayed by the graph's x-axis and y-axis. In order to facilitate a third dimension into the traditional scatter graph, the circle's diameter is altered. The relative diameter of a circle at one point compared to a circle at another point corresponds to the relative distance of the data in the third dimension.
Scalar values in the third dimension are entered by choosing the "Values" item from the task pop up button and then entering scalar values into the resulting table. In addition, the scalar values entered can also be displayed textually at the corresponding point by using the Preferences tool and turning on the display of the value. That preference tool also includes a scale parameter which acts to uniformly increase and decrease the relative sizes of the bubbles in order to accentuate the third dimension or make it more diminutive.
A bubble graph is a qualitative representation much like a pie graph. That is: the coordinate of the circle's diameter is not displayed nor is it represented by an axis. Instead, the viewer is left to view proportions of circle diameters. The third dimension is unrelated to the graph and its axes display. As such, do not try to align a circle's circumference with the displayed axis or think there is a relationship. Rather disassociate the circle's diameter with the displayed axis.
An arbitrary label (text) can also be displayed at each point. Those labels are entered by choosing the "Labels" item from the task pop up button and then entering text into the resulting table. The display of those labels is controlled by the Preferences tool.
Note the nature of the table entry. 2D Data points, scalar values and labels are each entered into their own table. Sometimes, a table is organized in columns of x-value, y-value, scalar and text label each repeated in that order to accommodate multiple curves (bubble data). In this current implementation, the added dimension and labeling are not interleaved into one table by design to prevent presenting overwhelming amount of features during data entry.
Through the use of Skins, the circle can be any supported graphic such as a square or polygon. See the Graph IDE manual for a description on setting the point tag marker.
Technical Note: Lets say the values for the third dimension are in the range of zero to one. The bubble at value zero will have a circle diameter that is non-zero and is of a minimum nominal value that corresponds to the diameter of the circles in the scatter graph representation. Then the circle's diameters increase from that minimum diameter value to a maximum diameter value that corresponds to the value of one. That is so that all points are marked by a circle. Thus when locating the value of zero, look for the minimum diameter circle, not a zero diameter circle.