What Mistake I am making in the code

I want to randomly pick two numbers from [39 25 91 71] swap it. and use while loop so that it swaps continuely until the vector is sorted. and display the sorted vector.

function out = sortbyrandomswaps(n)
x = 0; 
y = 0;
while ~ all(diff(n)>=0)
	x = n(randi(numel(n)));
	y = n(randi(numel(n)));
	x = a;
	y = x;
	a = y;
end
out = all(diff(n)>=0);

Answer 1

[Yongjian Feng]

Maybe this:

sortbyrandomswaps([5 4 3 2 1]);

function out = sortbyrandomswaps(n)

while ~ all(diff(n)>=0)
    idx1 = randi(numel(n));
    idx2 = randi(numel(n));
    a = n(idx2);
    n(idx2) = n(idx1);
    n(idx1) = a;

    disp(n);  % for debug only. Remove it if everything works.
end

out = all(diff(n)>=0);
end

Answer 2

[Steven Lord]

FYI you can perform a swapping operation in one step without needing an explicit temporary:

x = (1:10).^2

x = 1×10

1 4 9 16 25 36 49 64 81 100

toSwap = [4 7]

toSwap = 1×2

4 7

x(toSwap) = x(flip(toSwap)) % key step

x = 1×10

1 4 9 49 25 36 16 64 81 100

You could generalize this a bit if you wanted to swap a series of elements.

toSwap2 = [2 5 3 8 1];
x(toSwap2) = x(circshift(toSwap2, 1))

x = 1×10

64 1 25 49 4 36 16 9 81 100

The second element of x goes to position 5, the fifth to position 3, the third to position 8, the eighth to position 1, and the first to position 2.