MATLAB: Sorting a custom enumeration

enumerationsMATLABoopsort

For various reasons, I want to be able to define an enumeration. This enumeration will have some properties. I'd also like to be able to use it as a key. 
Undefined function 'sort' for input arguments of type 'MyGreatEnum'.
However, methods like 'unique' don't work, which is strange for me, as there is clearly a well defined set of unique enums in a list of enums, that are from the same class.
Any ideas?
i.e. I'd like to do
events
events = 
  2×1 MyGreatEnum enumeration array
    MyGreatEnum1 
    MyGreatEnum2
    
unique(events) 
Error using sort
Undefined function 'sort' for input arguments of type 'MyGreatEnum'.
Error in unique>uniqueR2012a (line 211)
            sortA = sort(a);
Error in unique (line 103)
    [varargout{1:nlhs}] = uniqueR2012a(varargin{:});

Best Answer

You should be able to sort your enumeration class if you derive it from a numeric class:
classdef myGreatEnum < double
    enumeration
        myGreatEnum1 (1)
        myGreatEnum2 (2)
        myGreatEnum3 (3)
        myGreatEnum4 (4)
        myGreatEnum5 (5)
        myGreatEnum6 (6)
        myGreatEnum7 (7)
        myGreatEnum8 (8)
        myGreatEnum9 (9)
    end
end
>> events = [myGreatEnum.myGreatEnum1, myGreatEnum.myGreatEnum5, myGreatEnum.myGreatEnum2, myGreatEnum.myGreatEnum5];
>> unique(events)
ans = 
  1×3 myGreatEnum enumeration array
    myGreatEnum1    myGreatEnum2    myGreatEnum5
Personally, I don't like the way enumerations are implemented in matlab. I would recommend that you use ordinal categorical arrays instead of enums. 
>> events = categorical([1 5 2 5], 1:9, compose('MyGreatEnum%d', 1:9), 'Ordinal', true)
events = 
  1×4 categorical array
     MyGreatEnum1      MyGreatEnum5      MyGreatEnum2      MyGreatEnum5 
>> unique(events)
ans = 
  1×3 categorical array
     MyGreatEnum1      MyGreatEnum2      MyGreatEnum5
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