Each node contains a Position Panel containing a variable number of elements that get Geometry values such that each shows a data value as an annular bar in a circle. One can also specify the colors of the bars. The Panel.itemTemplate also includes a TextBlock that shows its actual value as well as the percentage that it represents of the whole Array of data values.
For more sophisticated charts within nodes, see the Canvas Charts sample.
It is sometimes useful to display a variable number of elements in a node by data binding to a JavaScript Array. In GoJS, this is simply achieved by binding (or setting) Panel.itemArray. The Panel will create an element in the panel for each value in the Array. More information can be found in the GoJS Intro.
The GoJS Geometry class controls the "shape" of a Shape, whereas the Shape.fill and Shape.stroke and other shape properties control the colors and appearance of the shape. For common shape figures, there are predefined geometries that can be used by setting Shape.figure. However one can also define custom geometries.
One can construct any Geometry by allocating and initializing a Geometry of at least one PathFigure holding some PathSegments. But you may find that using the string representation of a Geometry is easier to write and save in a database. Use the static method Geometry.parse or the Shape.geometryString property to transform a geometry path string into a Geometry object.
More information can be found in the GoJS Intro.