Clinical informaticians, also known as clinical informaticists, transform health care by analyzing, designing, implementing, and evaluating information and communication systems that enhance individual and population health outcomes, improve [patient] care, and strengthen the clinician-patient relationship.
An ellipse is defined by two points, each called a focus. (F1, F2 above). If you take any point on the ellipse, the sum of the distances to the focus points is constant. In the figure above, drag the point on the ellipse around and see that while the distances to the focus points vary, their sum is constant. The size of the ellipse is determined by the sum of these two distances.
While the focus of the line chart is still change in values over time, the focus of an area chart is to highlight the magnitude of values over time. The difference is subtle, but when you need to show things like how many trees have been clear cut from 1990 to 1995 versus 2000 to 2005, the area chart really shines.