gslope simply waits for you to click twice on a graph and computes the slope between those points. Logarithmic scaling is automatically accounted for.
I use this for myself and in teaching to find observed convergence rates from a graph.
Toby Driscoll (2019). gslope (https://www.mathworks.com/matlabcentral/fileexchange/3148-gslope), MATLAB Central File Exchange. Retrieved .
Waiting for download
Simple and good.