# How can to compute the following case?

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If there is a cell D and its size 6*9 and this cell contains matrices. (Attached)

in this line: svd(D{1,1}.'*D{1,2});

how can I change the indices of D to do the multiplication of all combinations of D but without repeat the similar combinations such as:

D{1,1}.'*D{1,2} and D{1,2}.'*D{1,1}

and exclude the similar indicies such as

D{1,1}.'*D{1,1} and so on ...

Then store all the results in "distance"

[U,S,V] = svd(D{1,1}.'*D{1,2});

distance = sqrt(sum(arrayfun(@(i)acos(S(i,i))^2,1:4)))

##### 2 Comments

### Accepted Answer

Torsten
on 18 Jul 2023

Moved: Torsten
on 18 Jul 2023

D = load("D.mat");

D = D.D;

n = size(D,1);

m = size(D,2);

distance = zeros(n,m,n,m);

for i=1:n

for j=1:m

for i1=1:n

for j1=1:m

[~,S,~] = svd(D{i,j}.'*D{i1,j1});

distance(i,j,i1,j1) = sqrt(sum(arrayfun(@(k)acos(S(k,k))^2,1:size(S,1))));

end

end

end

end

[M,I] = max(distance,[],'All')

[i,j,i1,j1] = ind2sub([n,m,n,m],I)

distance(6,9,6,8)

distance(6,8,6,9)

##### 0 Comments

### More Answers (1)

Chunru
on 18 Jul 2023

load(websave("D.mat", "https://www.mathworks.com/matlabcentral/answers/uploaded_files/1436693/D.mat"));

for i=1:size(D, 1)

for j=1:size(D, 2)

for i1=1:size(D, 1)

for j1=1:size(D, 2)

S{i,j,i1,j1} = D{i,j} - D{i1,j1};

end

end

end

end

whos

S{1, 2, 3, 4} % for example: D{1,2}-D{3,4}

##### 5 Comments

Torsten
on 18 Jul 2023

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