Traduction code Matlab

Bonjour à tous les amiiis,
Ne codant pas en matlab j'aimerai qu'on me traduise en language matheux quelques lignes dans le code ci dessous.
C'est un kmeans

Ce sont ces 5 lignes qui me pose problème une explication courte me suffira :

Code:

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 [val,labels] = max(bsxfun(@minus,centroids*X(i:lastIndex,:)',c2));
      loss = loss + sum(0.5*x2(i:lastIndex) - val');
 
      S = sparse(1:m,labels,1,m,k,m); % labels as indicator matrix
      summation = summation + S'*X(i:lastIndex,:);
      counts = counts + sum(S,1)';
    end
 
 
    centroids = bsxfun(@rdivide, summation, counts);

voici le code en entier

Code:

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function centroids = runkmeans(X, k, iterations)
 
  x2 = sum(X.^2,2);
  centroids = randn(k,size(X,2))*0.1;%X(randsample(size(X,1), k), :);
  BATCH_SIZE=1000;
 
 
  for itr = 1:iterations
    fprintf('K-means iteration %d / %d\n', itr, iterations);
 
    c2 = 0.5*sum(centroids.^2,2);
 
    summation = zeros(k, size(X,2));
    counts = zeros(k, 1);
 
    loss =0;
 
    for i=1:BATCH_SIZE:size(X,1)
      lastIndex=min(i+BATCH_SIZE-1, size(X,1));
      m = lastIndex - i + 1;
 
      [val,labels] = max(bsxfun(@minus,centroids*X(i:lastIndex,:)',c2));
      loss = loss + sum(0.5*x2(i:lastIndex) - val');
 
      S = sparse(1:m,labels,1,m,k,m); % labels as indicator matrix
      summation = summation + S'*X(i:lastIndex,:);
      counts = counts + sum(S,1)';
    end
 
 
    centroids = bsxfun(@rdivide, summation, counts);
 
    % just zap empty centroids so they don't introduce NaNs everywhere.
    badIndex = find(counts == 0);
    centroids(badIndex, :) = 0;
  end

Merci à vous !