# Compute correlations in 3D arrays

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julian gaviria am 6 Nov. 2023
Kommentiert: julian gaviria am 7 Nov. 2023
%Random matrices
A=randi(100,374,374);
A_ = eye(size(A,[1 2]));
A(ones(size(A))&A_)=NaN;
B=randi(100,374,374);
B_ = eye(size(B,[1 2]));
B(ones(size(B))&B_)=NaN;
The following code computes correlation coeficient and p value from matrices A, B:
nn=374;
temp= ~eye (nn);
ii_all_conn = find(temp>0);
ii_uptri_conn = find(triu(temp,1)> 0);
ii_lotri_conn = find(tril(temp,-1)> 0);
%Corr plots up entries
figure, plot(A(ii_uptri_conn), B(ii_uptri_conn),'o');
[r,p]= corr(A(ii_uptri_conn), B(ii_uptri_conn));
title(['Upper connections - r = ' num2str(r) ' (p ' num2str(p) ')']);
%Corr plots low entries
figure, plot(A(ii_lotri_conn), B(ii_lotri_conn),'o');
[r,p]= corr(A(ii_lotri_conn), B(ii_lotri_conn));
title(['Lower connections - r = ' num2str(r) ' (p ' num2str(p) ')']);
Can I compute the same correlation and p-value in multidimensional arrays? E.g.
A_3D=randi(100,374,374,10);
B_3D=randi(100,374,374,10);
In the output, the first r and p values would correpond to the Pearson coeficient of A(:,:,1), B(:,:,1). and the tenth r and p values correpond to the Pearson coeficient of A(:,:,10), B(:,:,10)
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### Akzeptierte Antwort

Dyuman Joshi am 7 Nov. 2023
Run a for loop through the 3rd dimension -
A_3D = randi(100,374,374,10);
B_3D = randi(100,374,374,10);
s = size(A_3D,3);
[ru, pu, rl, pl] = deal(zeros(s,1));
for k = 1:s
[ru(k), pu(k), rl(k), pl(k)] = correlation(A_3D(:,:,k), B_3D(:,:,k));
end
%Upper triangle values
[ru pu]
ans = 10×2
0.0029 0.4429 0.0032 0.3950 0.0069 0.0684 -0.0013 0.7218 -0.0056 0.1426 -0.0027 0.4775 -0.0026 0.4976 -0.0055 0.1459 -0.0012 0.7442 0.0031 0.4171
%Lower triangle values
[rl pl]
ans = 10×2
0.0007 0.8508 -0.0015 0.6969 -0.0113 0.0028 0.0065 0.0878 0.0001 0.9798 0.0064 0.0892 -0.0038 0.3129 -0.0029 0.4408 -0.0012 0.7495 0.0043 0.2520
function [Ru, Pu, Rl, Pl] = correlation(A, B)
A = modify(A);
B = modify(B);
temp= ~eye(size(A,[1 2]));
%% Logical indexing is faster than find()
ii_uptri_conn = triu(temp,1)> 0;
ii_lotri_conn = tril(temp,-1)> 0;
[Ru,Pu] = corr(A(ii_uptri_conn), B(ii_uptri_conn));
[Rl,Pl] = corr(A(ii_lotri_conn), B(ii_lotri_conn));
end
function in = modify(in)
temp = eye(size(in,[1 2]));
in(ones(size(in))&temp) = NaN;
end
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julian gaviria am 7 Nov. 2023
Great, thanks a lot @Dyuman Joshi

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