# How to find differences of 2 matrices which contain other matrices as elements?

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Ege Tunç on 13 Dec 2020
Answered: Jan on 15 Dec 2020
o1 = eye(3,3);
o6=[1 -1 0; 1 0 0; 0 0 1];
o3=[0 -1 0;1 -1 0 ;0 0 1];
o2=[-1 0 0 ;0 -1 0; 0 0 1];
o3m=[-1 1 0; -1 0 0 ; 0 0 1];
o6m=[0 1 0; -1 1 0 ; 0 0 1];
omxx=[0 -1 0;-1 0 0; 0 0 1];
omx=[-1 1 0; 0 1 0; 0 0 1];
omy=[1 0 0 ;1 -1 0 ;0 0 1];
omxmx=[0 1 0;1 0 0; 0 0 1];
omx2x=[1 -1 0; 0 -1 0; 0 0 1];
om2xx=[-1 0 0 ; -1 1 0; 0 0 1];
G={o1,o6,o3,o2,o3m,o6m,omxx,omx,omy,omxmx,omx2x,om2xx};
labelsG={"o1","o6","o3","o2","o3m","o6m","omxx","omx","omy","omxmx","omx2x","om2xx"};
H={o1,o2};
labelsH={"o1","o2"};
K=setdiff(G,H);
Here my code. I want to find differences of G and H as J=[o6,o3,o3m,o6m,omxx,omx,omy,omxmx,omx2x,om2xx]
But it's not working

Jan on 13 Dec 2020
Edited: Jan on 14 Dec 2020
function [AA, AI] = CellDiff(A, B)
nA = numel(A);
nB = numel(B);
M = false(1, nA); % Typo fixed, thanks Paul
for iA = 1:nA
for iB = 1:nB
if isequal(A{iA}, B{iB})
M(iA) = true;
break;
end
end
end
AI = find(~M);
AA = A(AI);
end
Paul on 14 Dec 2020
Should M be initialized to either zeros or false?

Jan on 15 Dec 2020
The main problem is the choice of the data representation. Using an indexed field would allow to call setdiff().
Data.o1 = eye(3,3);
Data.o6 = [1 -1 0; 1 0 0; 0 0 1];
Data.o3 = [0 -1 0;1 -1 0 ;0 0 1];
Data.o2 = [-1 0 0 ;0 -1 0; 0 0 1];
Data.o3m = [-1 1 0; -1 0 0 ; 0 0 1];
Data.o6m = [0 1 0; -1 1 0 ; 0 0 1];
Data.omxx = [0 -1 0;-1 0 0; 0 0 1];
Data.omx = [-1 1 0; 0 1 0; 0 0 1];
Data.omy = [1 0 0 ;1 -1 0 ;0 0 1];
Data.omxmx = [0 1 0;1 0 0; 0 0 1];
Data.omx2x = [1 -1 0; 0 -1 0; 0 0 1];
Data.om2xx = [-1 0 0 ; -1 1 0; 0 0 1];
G = {"o1","o6","o3","o2","o3m","o6m","omxx","omx","omy","omxmx","omx2x","om2xx"};
H = {"o1","o2"};
Now setdiff(G, H) get the difference directly. Afterwards you can use something like Data.(G{1}) to get the corresponding values.