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TESI DOCTORAL - La Salle

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6.2. Adapting consensus functions to soft cluster ensembles<br />

Oλ = Iλ T Iλ =<br />

⎛<br />

0 1<br />

⎞<br />

0<br />

⎜<br />

0<br />

⎜<br />

0<br />

⎜<br />

⎜1<br />

⎜<br />

⎜1<br />

⎜<br />

⎜1<br />

⎜<br />

⎜0<br />

⎝0<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

0<br />

0 ⎟<br />

0 ⎟ ⎛<br />

0 ⎟ 0<br />

0⎟⎝<br />

⎟ 1<br />

0 ⎟ 0<br />

1 ⎟<br />

1⎠<br />

0<br />

1<br />

0<br />

0<br />

1<br />

0<br />

1<br />

0<br />

0<br />

1<br />

0<br />

0<br />

1<br />

0<br />

0<br />

0<br />

0<br />

1<br />

0<br />

0<br />

1<br />

⎞<br />

0<br />

0⎠<br />

1<br />

0<br />

⎛<br />

1<br />

0<br />

1<br />

1<br />

1 0 0 0 0 0<br />

⎞<br />

0<br />

⎜<br />

1<br />

⎜<br />

1<br />

⎜<br />

⎜0<br />

= ⎜<br />

⎜0<br />

⎜<br />

⎜0<br />

⎜<br />

⎜0<br />

⎝0<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

0<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

0 ⎟<br />

0 ⎟<br />

0 ⎟<br />

0 ⎟<br />

0 ⎟<br />

1 ⎟<br />

1⎠<br />

0 0 0 0 0 0 1 1 1<br />

(6.9)<br />

In a fuzzy clustering scenario, the object co-association matrix can easily be derived by<br />

simply multiplying the transpose clustering matrix Λ by itself. Resorting again to our toy<br />

clustering example, the resulting object co-association matrix (denoted as OΛ) ispresented<br />

in equation (6.10).<br />

It is easy to see that OΛ is indeed a fuzzy adjacency matrix, as the statistical independence<br />

of the probabilities of assigning objects i and j to the same cluster allows to interpret<br />

its (i,j)th entry as the joint probability that objects i and j are placed in the same cluster<br />

by the clusterer. However, statistical independence does not hold for the elements of the<br />

diagonal of OΛ, as each object is always “co-clustered” with itself, which would require<br />

making the elements on the diagonal of OΛ equal to 1.<br />

168

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