How can I count the number of swaps that occur when sorting a vector?

I am trying to reveal the number of swaps that occur when I sort a vector as ascending and descending. What would I need to code to allow the program to display the number of times the numbers swapped to get the final vector.

Current code for reference:

function out = sum2(varargin)
% Function accepts variable number of inputs and sorts them into an array.
% This function includes help text, ascending and descending orders, number
% of swaps, and an issued error.
% a = input
% b = input in ascending order
% k = input in descending order
%
% See also VARARGIN, NARGIN, SORT, HELP, ERROR.
fprintf('Total number of inputs = %d\n',nargin);
nVarargs = length(varargin);
fprintf('Inputs in varargin(%d)\n',nVarargs)
for i = 1:nargin
  a = cell2mat(varargin);
  c = mat2str(a);
  b = sort(c,'ascend');
  k = sort(c,'descend'); 
end
input = c
ascending = b
descending = k

[Stephen23]

It might be possible to modify the Wagner-Fischer algorithm (for calculating the Levenshtein distance, or edit distance) to only count swaps of position:

https://www.mathworks.com/matlabcentral/answers/318477-find-the-most-similar-word-from-a-set-of-words#answer_248951

Possibly the only "robust" way to count the number of swaps is to implement your own sorting algorithm.

[Sophia Boucher]

Thanks!

Answer 1

[Rik]

If you mean how many steps the algorithm has taken, that is impossible and might change between Matlab releases. If you want to know the number of differing positions you can try some code like this:

 [a_sorted,index_a]=sort(a);
 swaps_a=sum(index_a~=(1:length(a)));

PS don't overwrite the function input with a variable, it is super useful.

[Sophia Boucher]

Thanks!