how to reverse a matrix (nxm) sorting?

Hello everyone,

I have a matrix of order n by m, I did the sorting using the function sort of matlab. My question is how to undo the sorting using the indices matrix. Thank you.

[xs, indices] = sort(x,2);

Answer 1

[Stephen23]

x = rand(3,5)

x = 3×5

0.6428 0.5405 0.0059 0.3771 0.6076 0.2188 0.6466 0.3516 0.8349 0.1247 0.7154 0.2137 0.6896 0.0731 0.6152

[xs, is] = sort(x,2)

xs = 3×5

0.0059 0.3771 0.5405 0.6076 0.6428 0.1247 0.2188 0.3516 0.6466 0.8349 0.0731 0.2137 0.6152 0.6896 0.7154

is = 3×5

3 4 2 5 1 5 1 3 2 4 4 2 5 3 1

Method one: NDGRID and SUB2IND:

sz = size(x);
[~,ic] = sort(is,2);
[ir,~] = ndgrid(1:sz(1),1:sz(2));
ix = sub2ind(size(x),ir,ic);
y = xs(ix)

y = 3×5

0.6428 0.5405 0.0059 0.3771 0.6076 0.2188 0.6466 0.3516 0.8349 0.1247 0.7154 0.2137 0.6896 0.0731 0.6152

isequal(x,y)

ans = logical
   1

Method two: FOR loop:

y = nan(size(x));
for k = 1:size(x,1)
    y(k,is(k,:)) = xs(k,:);
end
display(y)

y = 3×5

0.6428 0.5405 0.0059 0.3771 0.6076 0.2188 0.6466 0.3516 0.8349 0.1247 0.7154 0.2137 0.6896 0.0731 0.6152

isequal(x,y)

ans = logical
   1

[Amine Alrharad]

Amazing Stephen23! it worked perfectly, thank you a lot.

[Amine Alrharad]

Sorry that I accepted late!