SPSS® 12.0 Command Syntax Reference

ALSCAL 103
• By default, ALSCAL assumes a symmetric matrix of dissimilarities for ordinal-level
variables. Only values below the diagonal are used. The upper triangle can be left blank.
The 12 cities form the rows and columns of the matrix.
• The result is a classical MDS analysis that reproduces a map of the United States when
the output is rotated to a north-south by east-west orientation.
VARIABLES Subcommand
VARIABLES identifies the columns in the proximity matrix or matrices that ALSCAL reads.
• VARIABLES is required and can name only numeric variables.
• Each matrix must have at least four rows and four columns.
INPUT Subcommand
ALSCAL reads data row by row, with each case in the working data file representing a single
row in the data matrix. (VARIABLES specifies the columns.) Use INPUT when reading
rectangular data matrices to specify how many rows are in each matrix.
• The specification on INPUT is ROWS. If INPUT is not specified or is specified without
ROWS, the default is ROWS(ALL). ALSCAL assumes that each case in the working data file
represents one row of a single input matrix, and the result is a square matrix.
• You can specify the number of rows (n) in each matrix in parentheses after the keyword
ROWS. The number of matrices equals the number of observations divided by the number
specified.
• The number specified on ROWS must be at least 4 and must divide evenly into the total
number of rows in the data.
• With split-file data, n refers to the number of cases in each split-file group. All split-file
groups must have the same number of rows.
Example
ALSCAL VARIABLES=V1 to V7 /INPUT=ROWS(8).
• INPUT indicates that there are eight rows per matrix, with each case in the working data
file representing one row.
• The total number of cases must be divisible by 8.
SHAPE Subcommand
Use SHAPE to specify the structure of the input data matrix or matrices.
• You can specify one of the three keywords listed below.
• Both SYMMETRIC and ASYMMETRIC refer to square matrix data.
SYMMETRIC Symmetric data matrix or matrices. For a symmetric matrix, ALSCAL
looks only at the values below the diagonal. Values on and above the
diagonal can be omitted. This is the default.