You cannot define a class using the older class syntax (where you call the class function inside the class's constructor function) that subclasses a class defined using the newer class syntax (one defined using a classdef file.)
From the documentation: "It is not possible to create class hierarchies that mix classes defined before Version 7.6 and current class definitions that use classdef. Therefore, you cannot subclass an old class to create a version of the new class."
