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TESI DOCTORAL - La Salle

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F.9. Segmentation data set<br />

φ (NMI)<br />

1<br />

0.8<br />

0.6<br />

0.4<br />

0.2<br />

0<br />

10 0<br />

MINING<br />

CPU time (sec.)<br />

10 2<br />

CSPA<br />

EAC<br />

HGPA<br />

MCLA<br />

VMA<br />

BC<br />

CC<br />

PC<br />

SC<br />

Figure F.8: φ (NMI) vs CPU time mean ± 2-standard deviation regions of the soft consensus<br />

functions on the miniNG data collection.<br />

Indeed, the consensus clustering solutions they yield are statistically significantly better<br />

than those output by state-of-the-art consensus functions such as VMA (which is the<br />

least time consuming), CSPA or MCLA —see table F.8 for further details regarding the<br />

statistical significance of the differences between consensus functions. The fourth consensus<br />

function proposed (CC) also yields higher quality than VMA, CSPA and MCLA, but its<br />

time complexity is notably higher, due to the nature of the Condorcet voting method.<br />

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

CSPA ——— 0.0001 0.0001 × 0.0001 0.0015 0.0001 0.0114 0.0115<br />

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

HGPA 0.0001 0.0001 ——— 0.0041 0.0001 0.0001 0.0001 0.0001 0.0001<br />

MCLA 0.0001 0.0001 0.0001 ——— 0.0001 0.0025 0.0001 0.0185 0.0187<br />

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

BC 0.0051 0.0001 0.0001 0.0001 0.0038 ——— 0.0001 × ×<br />

CC 0.008 0.0001 0.0001 0.0001 0.0061 × ——— 0.0001 0.0001<br />

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

SC 0.0001 0.0001 0.0001 0.0001 0.0001 × × 0.0126 ———<br />

Table F.8: Significance levels p corresponding to the pairwise comparison of soft consensus<br />

functions using a t-paired test on the miniNG 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.9 Segmentation data set<br />

The results of the application of the nine soft consensus functions upon the Segmentation<br />

data set are described next. Figure F.9 presents the φ (NMI) vs CPU time mean ± 2-standard<br />

deviation regions employed for comparing them.<br />

Again, VMA is the most computationally efficient consensus function. The proposed<br />

preference voting based clustering combiners (PC and SC), together with MCLA and<br />

382

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