Random shuffle of vector elements without repeating

For my class, I have to create an anagram-type function that receives an input string, shuffles all the elements, and returns a new string of the shuffled letters. We are to use for loops and if statements; we can't use perms, randperm, or randsample. I have a good start on this:

outstr=zeros(size(instr));
for i=1:numel(instr)
    outstr(randi([1,numel(instr)]))=instr(randi([1,numel(instr)]));
end
char(outstr)

My question is how to avoid repetition. Right now my function works, but it will repeat elements and thus leave some out. I'm thinking an if statement, to compare the randomly selected index to what has already been selected, but I can't pound it out yet. Any help is appreciated.

Answer 1

[Jan]

You can sort a vector of random values. The sorting index does not contain repetitions.

Did you search for a shuffle algorithm in the internet already? Look for "Knuth" and "Yates".

[Janell Lopez]

This is what I see for Yates:

function shuffle(array) {
  var m = array.length, t, i;

    // While there remain elements to shuffle…
    while (m) {

      // Pick a remaining element…
      i = Math.floor(Math.random() * m--);

      // And swap it with the current element.
      t = array[m];
      array[m] = array[i];
      array[i] = t;
    }

    return array;

I'm not familiar with Javascript--what would the likenesses be for my instr and outstr? How can I divide up this code for a function with input/output arguments?

Thank you!