Without the specific code to replicate the plot diagram, I may not be able to provide an accurate solution.However, MATLAB's 'quiver' function can be used to plot an arrow indicating directional components. To determine the direction of increasing time in wave propagation plots, observe the sequence of curves. If the curves shift right as they ascend the y-axis, time increases to the right; if left, time increases to the left. Identify the direction of time increase, then use 'quiver' to draw an arrow from the first (lowest) curve to the last (highest), visually indicating the direction of time progression.
The following MATLAB documentation link provides more details on using the 'quiver' function: https://www.mathworks.com/help/matlab/ref/quiver.html
Additionally, you can refer to the following MATLAB answer thread for more information: https://www.mathworks.com/matlabcentral/answers/160487-how-can-i-draw-a-line-with-arrow-head-between-2-data-points-in-a-plot
Hope this helps!