Multidimensional Scaling Options
The Options dialog box allows you to select the initial configuration style, specify iteration and convergence criteria, and select standard or relaxed updates.
Initial Configuration. Choose one of the following alternatives:
- Simplex. Objects are placed at the same distance from each other in the maximum dimension. One iteration is taken to improve this high-dimensional configuration, followed by a dimension reduction operation to obtain an initial configuration that has the maximum number of dimensions that you specified in the Model dialog box.
- Torgerson. A classical scaling solution is used as the initial configuration.
- Single random start. A configuration is chosen at random.
- Multiple random starts. Several configurations are chosen at random, and the configuration with the lowest normalized raw stress is used as the initial configuration.
- Custom. You select variables that contain the coordinates of your own initial configuration. The number of variables selected should equal the maximum number of dimensions specified, with the first variable corresponding to coordinates on dimension 1, the second variable corresponding to coordinates on dimension 2, and so on. The number of cases in each variable should equal the number of objects.
Iteration Criteria. Specify the iteration criteria values.
- Stress convergence. The algorithm will stop iterating when the difference in consecutive normalized raw stress values is less than the number that is specified here, which must lie between 0.0 and 1.0.
- Minimum stress. The algorithm will stop when the normalized raw stress falls below the number that is specified here, which must lie between 0.0 and 1.0.
- Maximum iterations. The algorithm will perform the number of specified iterations, unless one of the above criteria is satisfied first.
- Use relaxed updates. Relaxed updates will speed up the algorithm; these updates cannot be used with models other than the identity model or used with restrictions.
To Specify Multidimensional Scaling Options
This feature requires SPSS® Statistics Professional Edition or the Categories option.
- From the menus choose:
- Make the appropriate selections in the Data Format dialog box and click Define.
- In the Multidimensional Scaling dialog box, click Options.