How can I return a vector sorting from least to greatest without using the "sort" command?

If you a given a vector v=[4 2 7 4 12 9] how can I return this vector sorted from least to greatest without using the "sort" command. Is there a way of achieving this using loops?

[Adam]

Obviously you can write your own sort function of various types in any language, including Matlab. It sounds like an algorithmic problem more so than a Matlab one though. If you can put together a pseudo-code sort algorithm then converting that to Matlab language should not pose any difficulty and people here can help if it does.

Why do you not want to use 'sort' though. It sounds like the type of constraint that would be placed on a homework question so obviously one you are expected to figure out yourself!

[S]

What kind of pseudo code can I use for this? I have already tried using the < and > commands and I even tried using for loops. I don't know where I'm going wrong.

[Adam]

Well it depends what your purpose is in doing this. Obviously you can build up code yourself from something basic like:

if v(2) < v(1)
   tmp = v(1);
   v(1) = v(2);
   v(2) = tmp;
end

which swaps the first two elements around. A for or while loop is essentially just a generalisation of an if statement.

Sorting algorithms are amongst the most fundamental algorithms around though even though nowadays most people just use built-in ones instead of reinventing their own.

Any number of websites will no doubt give you either pseudo-code or code in some other language that you can convert to Matlab.

Writing your own algorithm will help you understand better though which I assume is the purpose of doing it without using the built-in sort.

[Jessica Avellaneda]

Hi! I would like to know how could you that if I want the vector sorting from GREATEST to LEAST without using the "sort", "min", "max" commands.

Thank you!

[Image Analyst]

Jessica, then you'd have to manually write your own version of sort, min and max. No one here wants to do that since there are already built in functions for that. The only people who say they need to do things manually without using the full power of built-in MATLAB functions are students doing homework assignments. And in that situation of course, we cannot provide the code (even if we did want to write it) because students are not allowed to turn in someone elses work as their own. I'm sure you can find pseudocode for sorting on Wikipedia or elsewhere. So good luck. If you still need help, see the following links:

How do I get help on homework questions on MATLAB Answers? - MATLAB Answers - MATLAB Central

Does the MathWorks provide any online homework assistance for students? - MATLAB Answers - MATLAB Central

What can be programmed "without any built-in functions" ? - MATLAB Answers - MATLAB Central

https://en.wikipedia.org/wiki/Sorting_algorithm

Answer 1

[Image Analyst]

Algorithms you can follow are given here: http://en.wikipedia.org/wiki/Sorting_algorithm

Answer 2

[Star Strider]

Probably the easiest way:

v=[4 2 7 4 12 9];

for k1 = 1:length(v)
    [sv(k1),ix] = min(v);       % Find Minimum & Index
    v(ix) = [];                 % Set Previous Minimum To Empty
end
v = sv                          % Output

[Brandon Marlowe]

Hi Star Strider,

Can you explain how "[sv(k1),ix]" indexes the value? I'm a little confused about that. Also, I came across this code while searching for a solution to the problem I was stumped on.

Thanks!

[Image Analyst]

It goes along building up sv by extracting the min from the vector (or what remains of it). Once the min of all the values has been extracted and stored in sv, it is deleted from the v vector so that it can't be found anymore. So basically at each step you're just pulling out the min of the remaining, and shrinking, vector "v" until all values have been examined and transferred to sv.

[Brandon Marlowe]

Ahhhhh, thank you very much!

[Diekoloreoluwa Ogundana]

could you explain the addition of 'ix' ?

Answer 3

[Sean de Wolski]

One of the guys we play cards with sorts this way. Makes for long games but works for a small number of cards

v = [4 2 7 4 12 9];
while 1
  idx = randperm(numel(v));
  if issorted(v(idx))
      vsort = v(idx);
      break
  end
end

[James Tursa]

LOL. Love this one ...