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Asked by Alvi Syahrin on 5 May 2013

I'm working with k-means in matlab. Here is my code:

load cobat.txt; % read the file

k=input('Enter a number: '); % determine the number of cluster isRand=0; % 0 -> sequeantial initialization % 1 -> random initialization

[maxRow, maxCol]=size(cobat); if maxRow<=k, y=[m, 1:maxRow]; else % initial value of centroid if isRand, p = randperm(size(cobat,1)); % random initialization for i=1:k c(i,:)=cobat(p(i),:) ; end else for i=1:k c(i,:)=cobat(i,:); % sequential initialization end end

temp=zeros(maxRow,1); % initialize as zero vector u=0; while 1, d=DistMatrix3(cobat,c); % calculate the distance [z,g]=min(d,[],2); % set the matrix g group

if g==temp, % if the iteration doesn't change anymore break; % stop the iteration else temp=g; % copy the matrix to the temporary variable end for i=1:k f=find(g==i); if f % calculate the new centroid c(i,:)=mean(cobat(find(g==i),:),1) end end c sort(c) end y=[cobat,g]

"cobat" is the file of mine. Here it looks:

65 80 55 45 75 78 36 67 66 65 78 88 79 80 72 77 85 65 76 77 79 65 67 88 85 76 88 56 76 65

"c" is the variable of centroid (the central of the cluster) per each cluster. "g" is the variable to show the cluster number. The problem is, I want to sort/fit the cluster number (small to big) based on the centroid (c). So, I try to sort(c), but it doesn't affect to the cluster number (g).

When I try to sort(g), it's sorted just not like what I want. I want the cluster number is sorted based on the centroid. Example; when I run the code with k=3, here is the final centroid

73.0000 79.0000 70.6667 %C 1 58.3333 73.3333 84.6667 %C 2 36.0000 67.0000 66.0000 %C 3

When I sort it, the number cluster is also "sorted",

36.0000 67.0000 66.0000 %C 3 58.3333 73.3333 70.6667 %C 2 73.0000 79.0000 84.6667 %C 1

I want it the number cluster is fit, like this.

36.0000 67.0000 66.0000 %C 1 58.3333 73.3333 70.6667 %C 2 73.0000 79.0000 84.6667 %C 3

This seems easy, but tricky. I couldn't figure out. Anyone have any idea to solve it?

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Answer by the cyclist on 5 May 2013

It sounds like you just need the sortrows() function.

Alvi Syahrin on 6 May 2013

Thank you for the answer. Where do I put that script? I have tried sortrows(c) or sortrows (g) or both, but it's just sorted not like what I want. I want the cluster number (g) is fit to the position of the cluster central (c). And when y=[cobat,g] is run, it doesn't have to be sorted. I just want the cluster number is sorted based on the position of the cluster central (c). You have any idea? ^_^

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