A problem with K-means Clustering

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Emanuele Gandolfi 2022-6-14

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https://ww2.mathworks.cn/matlabcentral/answers/1740240-a-problem-with-k-means-clustering

评论： Cris LaPierre 2022-6-14

X = rand(1482,74);
nCluster = 12;
[idx,sumd] = kmeans(X,2);
%%
for pp = 3 : nCluster
[~, index_max_cluster] = max(sumd);
       max_wcss_cluster = X(idx==index_max_cluster, :);
        
       [idx,sumd] = kmeans(max_wcss_cluster,2);
end
The logical indices in position 1 contain a true value outside of the array bounds.

'X' appears to be both a function and a variable. If this is unintentional, use 'clear X' to remove the variable 'X' from the workspace.

I need to bisecting K-means to a dataset, but I can't resolve this error. Maybe it's because I have to merge all the data into a cluster first?

How can I solve?

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采纳的回答

Cris LaPierre 2022-6-14

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Perhaps you could describe what you think your code is doing?

One thing to be aware of - outputs are determined by position, not variable name. If you want to capture sumd as an output of kmeans, it is captured in the third output.

[idx,C,sumd] = kmeans(___)

That would look like this

X = rand(1482,74);
[idx,C,sumd] = kmeans(X,2);

The error you are getting is because you are using idx==index_max_cluster, but since the dimensions don't match (idx is 758x1 while index_max_cluster is 1x74), implicit expansion is turing the comparison into a 758x74 matrix. When used to index X, the matrix is turned into a vector of 758*74=56092 elements. However, X only has 1482 elements. It is the combination of these size mismatches that is generating the error.