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SPSS® 12.0 Command Syntax Reference

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1282 PROXIMITIES<br />

0, 1, 1, 0, 0 for case 2 (where 1 indicates presence and 0 indicates absence), the contingency<br />

table is as follows:<br />

Case 2 characteristics<br />

Present Absent<br />

Case 1 characteristics<br />

Present 2 1<br />

Absent 0 2<br />

The contingency table indicates that both cases are present for two variables (W and X),<br />

both cases are absent for two variables (V and Y), and case 1 is present and case 2 is absent<br />

for one variable (Z). There are no variables for which case 1 is absent and case 2 is present.<br />

The available binary measures include matching coefficients, conditional probabilities,<br />

predictability measures, and others.<br />

Matching Coefficients. Table 1 shows a classification scheme for PROXIMITIES matching<br />

coefficients. In this scheme, matches are joint presences (value a in the contingency table)<br />

or joint absences (value d). Nonmatches are equal in number to value b plus value c.<br />

Matches and nonmatches may be weighted equally or not. The three coefficients JACCARD,<br />

DICE, and SS2 are related monotonically, as are SM, SS1, and RT. All coefficients in Table<br />

1 are similarity measures, and all except two (K1 and SS3) range from 0 to 1. K1 and SS3<br />

have a minimum value of 0 and no upper limit.<br />

Table 1 Binary matching coefficients in PROXIMITIES<br />

All matches included<br />

in denominator<br />

Equal weight for<br />

matches and nonmatches<br />

Double weight for<br />

matches<br />

Double weight for<br />

nonmatches<br />

Joint absences excluded<br />

from denominator<br />

Equal weight for<br />

matches and nonmatches<br />

Double weight for<br />

matches<br />

Joint absences<br />

excluded from<br />

numerator<br />

Joint absences<br />

included in<br />

numerator<br />

RR SM<br />

JACCARD<br />

DICE<br />

SS1<br />

RT

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