# How can to compute the following case?

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M on 18 Jul 2023
Moved: Torsten on 18 Jul 2023
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 CommentsShow NoneHide None
Chunru on 18 Jul 2023
Can you give an example of your data D?
M on 18 Jul 2023
@Chunru I attached the file

Torsten on 18 Jul 2023
Moved: Torsten on 18 Jul 2023
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')
M = 1.5695
I = 2592
[i,j,i1,j1] = ind2sub([n,m,n,m],I)
i = 6
j = 9
i1 = 6
j1 = 8
distance(6,9,6,8)
ans = 1.5695
distance(6,8,6,9)
ans = 1.5695

### More Answers (1)

Chunru on 18 Jul 2023
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
Name Size Bytes Class Attributes D 6x9 15984 cell S 6x9x6x9 863136 cell cmdout 1x33 66 char i 1x1 8 double i1 1x1 8 double j 1x1 8 double j1 1x1 8 double
S{1, 2, 3, 4} % for example: D{1,2}-D{3,4}
ans = 6×4
-0.0068 0.1359 0.2272 0.2585 -0.5386 0.0657 0.4552 0.5899 0.2370 0.1540 0.0995 0.0803 0.1061 0.0122 -0.0485 -0.0696 0.0210 -0.0793 -0.1435 -0.1655 -0.0087 -0.1109 -0.1761 -0.1985
Torsten on 18 Jul 2023
Are you sure all cell matrices directions{i,j} have the same number of columns ? The distance formula only applies under this condition.
M on 18 Jul 2023
Hi @Torsten, I edited the question, could you please suggest a solution