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Problems with kmeans clustering

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sam  CP
sam CP on 31 Mar 2017
Commented: sam CP on 3 Apr 2017
OI have used the following code to segment the attached image. But each iteration on the same image shows different result. How can i solve this by using rng('default'); ?
  2 Comments
Adam
Adam on 31 Mar 2017
You should just need to explicitly set the seed (either to 'default' I guess or to any seed of your choice) before each call to kmeans if you want the same result each time.
sam  CP
sam CP on 31 Mar 2017
Edited: sam CP on 31 Mar 2017
%k-means clustering algorithm
imData = reshape(Y,[],1);
imData = double(imData);
[IDX nn] = kmeans(imData,'default');
imIDX = reshape(IDX,size(Y));
figure, imshow(imIDX,[]),title('Image after applying k-means Clustering Algorithm');
Where can i apply the rng('default'); ?

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Accepted Answer

the cyclist
the cyclist on 31 Mar 2017
Edited: the cyclist on 31 Mar 2017
Looking at your code, you should be able to put the line
rng('default')
literally anywhere before the call to kmeans, because you do not call any other random number functions. But the safest bet might be to call it in the line just before the call to kmeans, in case you do something differently later.
But, also, I don't think you put 'default' in the actual kmeans call. So it should be like this ...
%k-means clustering algorithm
imData = reshape(Y,[],1);
imData = double(imData);
rng('default')
[IDX nn] = kmeans(imData);
imIDX = reshape(IDX,size(Y));
figure, imshow(imIDX,[]),title('Image after applying k-means Clustering Algorithm');
  10 Comments
Image Analyst
Image Analyst on 31 Mar 2017
Yeah, but let's put "works" in quotation marks because kmeans() is not a good method for finding brain tumors. Imagine what your algorithm would find for class 4 if there were no tumor present, or a very small one. Yeah, see what I mean?
sam  CP
sam CP on 3 Apr 2017
I have already found that the kmeans clustering method can't be detect the tumor when it is very small.

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