CRITERIA Subcommand (PREFSCAL command)

You can use CRITERIA to set the dimensionality and criteria for terminating the algorithm. You can specify one or more of the following keywords:

DIMENSIONS(min,max). Minimum and maximum number of dimensions. By default, PREFSCAL computes a solution in two dimensions. The minimum and maximum number of dimensions can be any integer between 1 and the number of objects minus 1 inclusive, as long as the minimum is less than or equal to the maximum. PREFSCAL starts computing a solution in the largest dimensionality and reduces the dimensionality in steps of one, until the lowest dimensionality is reached. Specifying a single value represents both minimum and maximum number of dimensions; thus, DIMENSIONS(4) is equivalent to DIMENSIONS(4,4).

MAXITER(n). Maximum number of iterations. By default, n=5000, specifying the maximum number of iterations that are performed while one of the convergence criteria below (DIFFSTRESS and MINSTRESS) is not reached. Decreasing this number might give less accurate results, but will take less time. The value n must have a non-negative integer value.

DIFFSTRESS. Convergence criterion. PREFSCAL minimizes the goodness-of-fit index “penalized Stress.” By default, PREFSCAL stops iterating when the relative difference in consecutive penalized Stress values is less than or equal to 0.000001. To obtain a more accurate solution, you can specify a smaller value. The specified value must be nonnegative.

MINSTRESS. Minimum Stress value. By default, PREFSCAL stops iterating when the penalized Stress value itself is small (that is, less than or equal to 0.001). To obtain a more accurate solution, you can specify a smaller value. The specified value must be nonnegative.

Example

PREFSCAL var01 TO var15 
  /CRITERIA = DIMENSIONS(2,4) MAXITER(10000) DIFFSTRESS(1.0E-8).
  • The maximum number of dimensions equals 4, and the minimum number of dimensions equals 2. PREFSCAL computes a four-dimensional, three-dimensional, and two-dimensional solution, respectively.
  • The maximum number of iterations is set to 10000.
  • The relative difference in penalized Stress convergence criterion is sharpened to 1.0E-8.