PROPERTIES Subcommand (PROXMAP command)

[/PROPERTIES [VARIABLES = varlist]
    [FUNCTION = {LINEAR }]
               {SPLINE** [DEGREE = {2*}] }
                                   {n }
                         [INKNOTS = {2*}]
                                    {n }
                         [PLACEMENT = {INTERVALS* }]
                                      {PERCENTILES}
                         [MONOTONIC = {YES*}]
                                      {NO  }
               {ORDINAL [APPROACH = {KEEPTIES}] }
                                    {UNTIE   }
               {NOMINAL}
[/PROPERTIES ...]

The PROPERTIES subcommand specifies one or more property variables (external variables) to be fitted into the common space. These variables are not used to determine the configuration but are instead projected onto the final solution space for interpretive purposes.

This subcommand may be repeated, allowing different sets of properties to be transformed with different specifications.

The PROPERTIES subcommand has the following uses:

Add interpretive variables to an object configuration.
Explore how external variables relate to the dimensions without influencing the underlying configuration.
Supplement the ATTRIBUTES subcommand, which actively restricts the configuration.
Specify nominal variables as either attribute variables or property variables. But they are handled differently depending on their role.

VARIABLES

Specifies a list of property variables in the active dataset.

FUNCTION

Specifies the transformation to apply to the property variables. This includes the following options:

Option	Description
`LINEAR`	Applies a linear transformation. The transformed values remain proportional to the original attribute values.
`SPLINE`	This is the default value. It applies a smooth piecewise polynomial transformation. Spline transformations include the following additional options. `DEGREE = n`indicates the degree of the polynomial pieces. The value must be an integer in the interval [0, n], where `n` is the number of distinct values in the property. The default value is 2. `INKNOTS = n` indicates the number of interior knots. The value must be an integer in the interval [0, n], where `n` is the number of distinct property values minus two. If `INKNOTS` is greater than this number, it is set to this maximum. The default value is 2. The maximum for the sum of `DEGREE` and `INKNOTS` is the number of distinct property values minus 1. If this maximum is exceeded, the `DEGREE` specification is adapted. `PLACEMENT = INTERVAL` indicates that knots are placed at evenly spaced intervals over the property range. `PLACEMENT = PERCENTILES`indicates that knots are placed at percentile points based on the distribution of property values. `MONOTONIC = YES` is the default setting. This indicates that the transformation must be monotonic. `MONOTONIC = NO`indicates that monotonicity is not required.
`ORDINAL`	Applies an ordinal transformation that preserves only the rank order of the property values. Tied values include the following options: `APPROACH = UNTIE` is the default option. With this option, tied values become separated during transformation. `APPROACH = KEEPTIES` indicates that ties in the original data are retained in the transformation.
`NOMINAL`	This parameter treats the property values as unordered categories. Only grouping information is preserved. The transformation results in a set of multidimensional coordinates. Each category is represented by a point located at the centroid (average position) of the objects that belong to that category in the final configuration space.

Example

GET FILE’kinship.sav’.
PROXMAP
 /SOURCEID DATA = aunt brother cousin daughter father granddaughter grandfather grandmother grandson
                  mother nephew niece sister son uncle
 /PROPERTIES VARIABLES = degree generation FUNCTION = ORDINAL
 /PROPERTIES VARIABLES = gender FUNCTION = NOMINAL.

In this example, proximities between kinship terms are analyzed, represented in the data file by variables aunt through uncle. Since the kinship terms variables represent proximities, the DATA subcommand is required.
Three properties variables are specified: degree, generation, and gender.
The properties, degree and generation are ordinally transformed, and tied values are allowed to be untied by default.
The attribute gender is nominally transformed.