MEASURE Subcommand (PROXIMITIES command)

MEASURE specifies the similarity, dissimilarity, or distance measure that PROXIMITIES computes. Three transformations are available:

ABSOLUTE. Take the absolute values of the proximities. Use ABSOLUTE when the sign of the values indicates the direction of the relationship (as with correlation coefficients) but only the magnitude of the relationship is of interest.

REVERSE. Transform similarity values into dissimilarities, or vice versa. Use this specification to reverse the ordering of the proximities by negating the values.

RESCALE. Rescale the proximity values to a range of 0 to 1. RESCALE standardizes the proximities by first subtracting the value of the smallest proximity and then dividing by the range. You would not usually use RESCALE with measures that are already standardized on meaningful scales, as are correlations, cosines, and many binary coefficients.

PROXIMITIES can compute any one of a number of measures between items. You can choose among measures for interval data, frequency-count data, or binary data. Available keywords for each type of measures are defined in the following sections.

  • Only one measure can be specified. However, each measure can be specified with any of the transformations ABSOLUTE, REVERSE, or RESCALE. To apply a transformation to an existing matrix of proximity values without computing any measures, use keyword NONE (see ).
  • If more than one transformation is specified, PROXIMITIES handles them in the order listed above: ABSOLUTE, REVERSE, and then RESCALE (regardless of the order in which they are specified).
  • Each entry in the resulting proximity matrix represents a pair of items. The items can be either cases or variables, whichever is specified on the VIEW subcommand.
  • When the items are cases, the computation for each pair of cases involves pairs of values for the specified variables.
  • When the items are variables, the computation for each pair of variables involves pairs of values for the variables across all cases.

Example

PROXIMITIES A B C
  /MEASURE=EUCLID REVERSE.
  • MEASURE specifies a EUCLID measure and a REVERSE transformation.