is an abbreviated
version of the full PINDIS procedure. As in
the full version, it takes as its input data a number of configurations,
which will normally be the result of some previous scaling analysis,
although any technique giving dimensional output (such as factor or components
analysis) is also suitable. The points in each of the configurations must
be the same although the dimensionality of the spaces is allowed to differ
between configurations.
Instead
of estimating the Centroid configuration, the user may input an external reference (or hypothetical) configuration
of the same stimuli in the same number of dimensions (such as an original study
of which the data are replications), or repeat the configuration for one of the
subjects to which the others should be compared, introduced by READ
HYPOTHESIS. The higher order models in PINDIS allow that subjects may
systematically distort this basic configuration.The first mode of distortion is analogous to that of the INDSCAL model in that subjects, in arriving at
their perceptual spaces, are thought of as applying differential weights to the
dimensions of the group space (the centroid). The maximum
number of dimensions in any one configuration is given in the DIMENSIONS
statement, the number of configurations, by N OF SUBJECTS. The number of
points in the configuration is given by N OF STIMULI and the data are
read by the READ CONFIGS command. The INPUT FORMAT specification,
if used, should read the longest row of the configurations. By default, free
format input is assumed. INPUT
COMMANDS Keyword
Function NOTES PRINT (to main output file) By
default, CENTROID only is applied.
PLOT
(to main output file) PUNCH
options
(to secondary output file) PROGRAM
LIMITS
See also
The basic Procrustean model relies on
the assumption that that MDS configurations are unique under translation, rotation, and reflection.
The program takes each pair of configurations in turn
and, by applying these transformations, brings them into maximum conformity with
each other. This effectively eliminates any differences in the configurations
due to the conventions of the program producing them and
leaves the substantive differences - due to random error and
differential cognition. A centroid configuration is formed simply by taking the average position
of each point over all the configurations. The model implies that individual "subjects"
(or data-sources) make no
systematic distortions of the group space (the centroid).
N OF STIMULI [number]
Number of stimuli in the analysis
N OF SUBJECTS [number]
Number of subject configurations to be
compared
in the analysis
DIMENSIONS [number]
Maximum number of dimensions in
any one
configuration
LABELS [followed by a series Optionally identify
the stimuli,
of
labels (<= 65 chars) followed by the subjects, as
each on
a separate required. All labels should
be
line] entered,
without
omissions.
READ CONFIGS Input
the subject configurations
immediately
following this command.
READ HYPOTHESIS (Optional)
Input a configuration to
use
as a reference for comparisons;
if
not present, the centroid
is
used by default.
1. The READ CONFIGS command is obligatory in PROCRUSTES.
2. READ MATRIX is not valid with PROCRUSTES.
Option
Form Description
CENTROID p x r
The centroid configuration is printed
at each phase, with the
results of applying
the basic similarity
transformations
P0
for each subject.
Option
Description
CENTROID
The CENTROID (or HYPOTHESIS) configuration,
whichever
is being used for reference,
is
plotted at each phase.
By
default, CENTROID only is applied.
Option
Description
CENTROID The
coordinates of the centroid
configuration
are output.
Maximum no. of subjects = 100
Maximum no. of stimuli = 100
Maximum no. of dimensions = 4