INITIAL Subcommand (PROXSCAL command)
INITIAL
defines
the initial or starting configuration of the common space for the
analysis. When a reduction in dimensionality is specified on the CRITERIA
subcommand, a derivation of coordinates
in the higher dimensionality is used as a starting configuration in
the lower dimensionality.
- You can specify one of the three keywords listed below.
- You can specify a variable list containing the initial configuration.
SIMPLEX. Simplex start. This specification is the default. PROXSCAL
starts by placing the objects in the configuration all at the same
distance of each other and taking one iteration to improve this high-dimensional
configuration, followed by a dimension-reduction operation to obtain
the user-provided maximum dimensionality specified in the CRITERIA
subcommand with the keyword DIMENSIONS
.
TORGERSON. Torgerson start. A classical scaling solution is used as initial configuration.
RANDOM. (Multiple)
random start. You can specify the number of random starts
(n). n is any positive integer. The random sequence can be
controlled by the RANDOM SEED
command and not by a subcommand within the PROXSCAL
command. Each analysis starts with a different
random configuration. In the output, all n final stress values are reported, as well as the initial
seeds of each analysis (for reproduction purposes), followed by the
full output of the analysis with the lowest stress value. The default
number of random starts is 1. Reduction of dimensionality—that
is, using a maximum dimensionality that is larger than the minimum
dimensionality—is not allowed within this option and the minimum
dimensionality is used, if reduction is specified anyway.
Instead of these keywords, a parenthesized IBM® SPSS® Statistics data file can be specified containing
the coordinates of the initial configuration. If the variable list
is omitted, the first MAXDIM
variables
are automatically selected, where MAXDIM
is the maximum number of dimensions requested for the analysis on
the CRITERIA
subcommand. Only
nonmissing values are allowed as initial coordinates.
Example
PROXSCAL object01 TO object17
/INITIAL=RANDOM(100).
- This example performs 100 analyses each, starting with different random configurations. The results of the analysis with the lowest final stress are displayed in the output.