When the quantity that depends on x and y has both magnitude and a direction it can be represented by an arrow whose length is proportional to the magnitude. The x-y plane can be broken into a regular grid and an arrow drawn in the plane, representing the direction and magnitude associated with each point on the grid—a vector plot. As we are associating two quantities, the magnitude and direction, or, equivalently, Δx and Δy, for each x-y pair, we can think of this type of plot as a 4D plot.
The previous figure is a vector field of a rotating flow. The exact appearance of the arrows will vary with the output terminal.