To find a Matlab source file that corresponds to the movie or figure that you are interested in, click on the link in the Book page and the name of the matlab file will appear in the window line with the extension .html.
Note that the Matlab source codes are organized by Chapters directories, to aid in locating the matching source code.
Some of the Matlab programs call function statements. The necessary function statements for a given program can be found in the same chapter directory.