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TESI DOCTORAL - La Salle

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F.7. MFeat data set<br />

φ (NMI)<br />

1<br />

0.8<br />

0.6<br />

0.4<br />

0.2<br />

0<br />

BALANCE<br />

10 0<br />

CPU time (sec.)<br />

CSPA<br />

EAC<br />

HGPA<br />

MCLA<br />

VMA<br />

BC<br />

CC<br />

PC<br />

SC<br />

Figure F.6: φ (NMI) vs CPU time mean ± 2-standard deviation regions of the soft consensus<br />

functions on the Balance data collection.<br />

performing consensus functions (CSPA, VMA, PC and SC) are not statistically significant.<br />

CSPA EAC HGPA MCLA VMA BC CC PC SC<br />

CSPA ——— 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001<br />

EAC 0.0001 ——— 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001<br />

HGPA 0.0001 0.0003 ——— 0.0419 0.0001 0.0004 0.0001 0.0001 0.0001<br />

MCLA 0.0291 0.0001 0.0001 ——— 0.0001 0.0001 0.0001 0.0001 0.0001<br />

VMA × 0.0001 0.0001 × ——— 0.0001 0.0001 0.0001 0.0001<br />

BC 0.0139 0.0001 0.0001 × × ——— 0.0044 0.0001 0.0001<br />

CC 0.0139 0.0001 0.0001 × × × ——— 0.0001 0.0001<br />

PC × 0.0001 0.0001 × × 0.0322 0.0322 ——— ×<br />

SC × 0.0001 0.0001 × × × × × ———<br />

Table F.6: Significance levels p corresponding to the pairwise comparison of soft consensus<br />

functions using a t-paired test on the Balance data set. The upper and lower triangular<br />

sections of the table correspond to the comparison in terms of CPU time and φ (NMI) ,<br />

respectively. Statistically non-significant differences (p >0.05) are denoted by the symbol<br />

×.<br />

F.7 MFeat data set<br />

The results of the soft consensus clustering experiments conducted on the MFeat data set<br />

are presented in this section. For this purpose, figure F.7 depicts the diagram displaying<br />

the φ (NMI) vs CPU time mean ± 2-standard deviation regions corresponding to the nine<br />

soft consensus functions compared, and table F.7 presents the results of the statistical<br />

significance t-paired tests that compares them pairwise.<br />

In time complexity terms, VMA is the best performing consensus function, closely followed<br />

by MCLA, HGPA, PC and SC (the two latter being statistically equivalent). Among<br />

the two proposed positional voting based consensus functions, BC is clearly more efficient<br />

than CC. This probably is due to the larger number of classes (i.e. candidates) in this data<br />

set, which makes CC more costly due to the exhaustive pairwise candidate confrontation<br />

380

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