Define a Multidimensional Scaling Model
The Model dialog box allows you to specify a scaling model, its minimum and maximum number of dimensions, the structure of the proximity matrix, the transformation to use on the proximities, and whether proximities are transformed within each source separately or unconditionally on the source.
Scaling Model. Choose from the following alternatives:
- Identity. All sources have the same configuration.
- Weighted Euclidean. This model is an individual differences model. Each source has an individual space in which every dimension of the common space is weighted differentially.
- Generalized Euclidean. This model is an individual differences model. Each source has an individual space that is equal to a rotation of the common space, followed by a differential weighting of the dimensions.
- Reduced rank. This model is a generalized Euclidean model for which you can specify the rank of the individual space. You must specify a rank that is greater than or equal to 1 and less than the maximum number of dimensions.
Shape. Specify whether the proximities should be taken from the lower-triangular part or the upper-triangular part of the proximity matrix. You can specify that the full matrix be used, in which case the weighted sum of the upper-triangular part and the lower-triangular part will be analyzed. In any case, the complete matrix should be specified, including the diagonal, though only the specified parts will be used.
Proximities. Specify whether your proximity matrix contains measures of similarity or dissimilarity.
Proximity Transformations. Choose from the following alternatives:
- Ratio. The transformed proximities are proportional to the original proximities. This is allowed only for positively valued proximities.
- Interval. The transformed proximities are proportional to the original proximities, plus an intercept term. The intercept assures all transformed proximities to be positive.
- Ordinal. The transformed proximities have the same order as the original proximities. You specify whether tied proximities should be kept tied or allowed to become untied.
- Spline. The transformed proximities are a smooth nondecreasing piecewise polynomial transformation of the original proximities. You specify the degree of the polynomial and the number of interior knots.
Apply Transformations. Specify whether only proximities within each source are compared with each other or whether the comparisons are unconditional on the source.
Dimensions. By default, a solution is computed in two dimensions (Minimum = 2, Maximum = 2). You choose an integer minimum and maximum from 1 to the number of objects minus 1 (as long as the minimum is less than or equal to the maximum). The procedure computes a solution in the maximum dimensions and then reduces the dimensionality in steps until the lowest is reached.
To Define a Multidimensional Scaling Model
This feature requires 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 Model.