Analyze g Line distance (F9)

You draw a line between two points by clicking on the graph once for each point, and then the program calculates the X distance (DX), the Y distance (DY), the derivative (DY/DX), the Y value where the line would cross the Y axis (C) and the length of the line (Dist).

You can move the line around by dragging its end points. If snap to plot is active before line distance is selected, the end points will snap to the nearest data point after dragging.