dm.cs.tu-dortmund.de/mlbits/cluster-kmeans-limitations/
Limitations of k-Means Clustering – Lecture Notes
starting conditions we keep {c,d}.
The optimum solution then has cost \(x^2/2\) , the bad solution has \(z^2/2\) .
So the ratio \(z^2/x^2\) can be made arbitrarily bad.
➜ in the worst case, a \(k\) -means solution [...] \smash {\mu _T-x}\mathstrut \right\rVert ^2 - \tfrac {|S|}{|S|-1}\left\lVert \smash {\mu _S-x}\mathstrut \right\rVert ^2 = \tfrac {1}{2} 4^2 - \tfrac {4}{3} 3^2 = 8 - 12 = -4 \end{align*}\]
➜ The standard [...]
If we have chosen \(a\) and \(d\) , it chooses the better solution with probability \(\frac{z^2}{x^2+z^2}\) .
Nearest Center Assignment is Not Optimal [ HaWo79 ; TeVa10 ]
The standard algorithm converges …