MATLAB: How to randomly swap 2 elements in an array

matrix arrayrandom

Suppose that I have the below array:
C= [1 6 5 10 1 2 11 8 2 7 3 7 9 9]
How can I swap randomly only the elements inside the bold numbers
Assume after swap 11 and 3 : C= [1 6 5 10 1 2 3 8 2 7 11 7 9 9]
or swap 10 and " " between 9 9: C= [1 6 5 1 2 11 8 2 7 3 7 9 10 9]

Best Answer

I'm going to assume at least one of the swap elements must be an number, and that the swapped numbers are allowed to have the same value (so you can some one 9 with another 9).
C=  [1     6     5    10     1     2    11     8     2     7     3     7     9     9];
bold=[1 5 6 9 10 12 13 14];
C_temp=cell(1,2*numel(C));
C_temp(2:2:end)=num2cell(C);
valid_idx=1:numel(C_temp);
valid_idx(bold*2)=[];
swap_idx=[1 1];%invalid output to enter the loop
while ~any(mod(swap_idx,2)==0) || ... %at least 1 needs to be a number
        swap_idx(1)==swap_idx(2) %the indices must be different
    swap_idx=valid_idx(randperm(numel(valid_idx),2));
end
%perform swap
C_temp(swap_idx)=C_temp(swap_idx(end:-1:1));
D=cell2mat(C_temp);
clc,disp(C),disp(D)
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