# How to sort a 3D matrix according to the value of each element?

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TA on 24 Aug 2021
Edited: Wan Ji on 24 Aug 2021
Hello,
I have a 3D matrix (attached). What I wish to accomplish is to sort this matrix, element by element, such that the highest value(s) are towards the bottom (i.e. last rows) when I visualize it and vice versa.
I have tried the sort/sortrows commands but haven't had much success with my current knowledge. If anyone can nudge me in the right direction, I'd be grateful.

Simon Chan on 24 Aug 2021
If I understand correctly, you would like the larger value(s) in the last rows and the largest one on the bottom right hand corner (last row and last column).
If this is not the case, the following code does not work.
clear; clc;
[Ny,Nx,Nz] = size(num);
sortnum = zeros(size(num));
for k = 1:Nz
data = num(:,:,k);
sortnum(:,:,k) = transpose(reshape(sort(data(:)),Nx,Ny));
end

Wan Ji on 24 Aug 2021
Edited: Wan Ji on 24 Aug 2021
I think you want make something gif to show how the numbers are sorted?
% sort show
% show bubbling
clc;clear
% a = num(1:32,:,:); clear num
a = rand(30,50,40);
[x,y,z] = meshgrid(1:size(a,1), 1:size(a,2), 1:size(a,3));
x = x(:);
y = y(:);
z = z(:);
Idx = sub2ind(size(a),x,y,z);
scatter3(x,y,z,10,a(Idx),'filled')
axis equal
% colr = gray;
colr = jet;
colr = colr(end:-1:1,:);
colormap(colr)
view(-163,-66)
for k = 1:1:size(a,1)
for r = size(a,1):-1:k+1
for i = 1:1:size(a,2)
for j = 1:1:size(a,3)
if(a(k,i,j)<a(r,i,j))
a([k,r],i,j) = a([r,k],i,j);
end
end
end
scatter3(y,x,z,10,a(Idx),'filled')
view(-163,-66)
xlabel('Dimension 2'); ylabel('Dimension 1'); zlabel('Dimension 3');
axis equal
colormap(colr); colorbar;
pause(0.001)
end
end