To open a history graph, in Display, select a view and click the Display how the value of a choice attribute has changed over time icon . In the bottom frame, from the Type list, select History Graph.
The x-axis shows time; the y-axis shows the number of elements.
The black line indicates the total number of elements, and the colored
areas indicate the number of elements that had a certain choice value.
In the following example, light blue indicates verified bugs and orange
indicates fixed but not verified bugs.
The total number of bugs increases almost constantly. Between positions A and B, the developers fix several bugs, and the height of the orange area increases. Between B and C, they verify that the bugs were handled correctly, and the orange area is replaced by light blue.
The white area below the black line indicates that some of the elements are created when changes are not logged, or that some of the elements had a choice attribute value that was removed.