Swapping values within a vector if the one after it is greater than the one before it.

Need help on some homework that I feel so close yet so far away on.

For example the 1st and 2nd entries in x. I need to swap the two entries if the first entry is larger than the second. and display what the final x-vector looks like.

 x = [1 -2 3 5 4 2]
 for k = 1:5;
    if x(k) > x(k+1)
        x(k) = x(k+1)
    elseif x(k) < x(k+1)
        x(k) = x(k)
    end

I haven't yet tried to display the final vector. However when I run this code it gives me some funky numbers. I don't know how to fix it, any suggestions?

Answer 1

[James Tursa]

To do the swap you could just use a two-element index vector. E.g.,

    if x(k) > x(k+1)
        x([k,k+1]) = x([k+1,k]);
    end

[Stephen23]

This is the more efficient solution for swapping two values.

Answer 2

[Kirby Fears]

First off, what you're doing isn't a swap. You're overwriting x(k) but what about x(k+1)? It's still retaining it's original value. Also, your else case doesn't do anything. This would be an iterative swap:

 x = [1 -2 3 5 4 2];

 for k = 1:numel(x)-1;
    if x(k) > x(k+1),
        temp = x(k);
        x(k) = x(k+1);
        x(k+1) = temp;
    end
 end

If your end goal is to sort X in increasing order, you could simply use the sort command...

 x = [1 -2 3 5 4 2];
 sort(x)
 ans =
    -2     1     2     3     4     5

Hope this helps.