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How to determine if an array of objects is part of an other array of objects?

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Tom Wenk
Tom Wenk on 23 May 2018
Commented: Jan on 24 May 2018
I have an array containing classdef-objects ( value class ) of the same class, but with different values for the properties.
A = [ objA, objB, objC, objD ];
Now I get another array with objects of the same class
B = [ objX, objY ];
Comparing objects with each other I can do by
isequal( objX, objA );
which returns true. Also objY is equal to objC.
Now like with numeric arrays (I think there it was any or ismember or just through vector operations) I want to do this kind of check:
isequal( A, B );
and it should return true, because all parameters I'm searching for (combined in array B) are present in A!
Using isequal on A and B returns 0 because not all objects are equal and this is the only function I found to compare objects.
Is there a secret function or workaround?
Thanks for your help! :)
Here is a MWE:
class 1 (prop arr contains objects of class 2)
classdef arrOfTests
end %properties
function obj = arrOfTests()
obj.arr = test.empty;
obj.arr(1) = test( 'One', 'Test', 1 );
obj.arr(2) = test( 'Two', 2, [1,2] );
obj.arr(3) = test( 'Three', 'Test', [1,2,3] );
end %function test (Constructor)
end %methods
end %classdef
class 2 (element of array in property of class 1)
classdef test
end %properties
function obj = test(propOne, propTwo, propThree)
obj.propOne = propOne;
obj.propTwo = propTwo;
obj.propThree = propThree;
end %function test (Constructor)
end %methods
end %classdef
example script to create the objects:
obj = arrOfTests();
compObj = test( 'Two', 2, [1,2] );
isequal( compObj, obj.arr ); % ans = 0; not equal
isequal( compObj, obj.arr(2) ); % ans = 1; is equal
%ismember( compObj, obj.arr ); % Error: Undefined operator '==' for input arguments of type 'test'...
%ismember( compObj, obj.arr(2) ); % Error: Undefined operator '==' for input arguments of type 'test'...
%all( ismember( compObj, obj.arr ) ); % Error: Undefined operator '==' for input arguments of type 'test'...

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Accepted Answer

Ameer Hamza
Ameer Hamza on 24 May 2018
You can do this using this statement
all(cellfun(@(x) any(x), arrayfun(@(x) arrayfun(@(y) isequal(x, y), A), B, 'UniformOutput', 0)'))
This will check whether all the values of B are present in A.
Tom Wenk
Tom Wenk on 24 May 2018
What it does is perfect, but is there also an other way to get there besides using for-loops?

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More Answers (1)

Jan on 24 May 2018
all(ismember(A, B))
Jan on 24 May 2018
Because I do not know, what the properties of your class are, while you have the class definition available already, it would be a waste of time, if I re-write what I guess might solve your problem. Please be so kind and post the MWE by your own. [EDITED - ah, I've found your code, thanks.]
I cannot estimate, if ismember with an overloaded eq is faster, but of course it would be nice and intuitive. Note that setdiff, setxor, unique and union might work directly also directly. Having a powerful implementation of the class, which works fluently with all the standard tools provided by Matlab, would be a great advantage. Perhaps a specific cellfun/arrayfun/arrayfun approach is some microseconds faster (but arrayfun is usually slower than a simple FOR loop!), having the standard set function can save you minutes or hours of programming and debug time.
On the other hand, a dedicated function could be much faster: all(ismember()) checks all elements. But if the first one is not matching already, most of the time is lost. I'd start with a loop:
function T = ContainsAll(A, B)
T = true;
nB = numel(B);
for iA = 1:numel(A)
AA = A.arr(iA);
for iB = 1:numel(B)
if ~isequal(AA, B.arr(iB))
T = false;
Darn. I'm too tired to work. This is a function. Of course a method would be nicer, because this is OOP. Sorry.

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