You have taken a video of an ice-skater moving left to right on your phone's screen. You decide to plot the data of position versus time, and send it to a friend who also wants to make a graph. (You both have the same Physics instructor with the same quirky homework). While you agree the left to right distance is positive, you make your graph based on the skater's distance from the LEFT edge, while your friend makes her graph as if distance is measured from the RIGHT edge of the camera screen. How do the graphs differ?