How to make a line move along the graph?

I have seen an awesome gif in this page of Wikipedia and I tried to redo it, nevertheless, I really don't know how to make this line (with a point) move along the graph.

https://pt.wikipedia.org/wiki/Derivada#/media/Ficheiro:Graph_of_sliding_derivative_line.gif

[Mathieu NOE]

hi

see : https://stackoverflow.com/questions/23688688/how-to-do-an-animated-plot-in-matlab