SPSS® 12.0 Command Syntax Reference

Matrix Input
CLUSTER 241
• The matrices produced by CLUSTER can be used by subsequent CLUSTER procedures or
by procedures PROXIMITIES and ALSCAL.
• Any documents contained in the working data file are not transferred to the matrix file.
• CLUSTER can read matrices written by a previous CLUSTER command or by PROXIMITIES,
or created by MATRIX DATA. When the input matrix contains distances between variables,
CLUSTER clusters all or a subset of the variables.
• Values for split-file variables should precede values for ROWTYPE_. CASENO_ and the
labeling variable (if present) should come after ROWTYPE_ and before VARNAME_.
• If CASENO_ is of type string rather than numeric, it will be considered unavailable and
a warning is issued.
• If CASENO_ appears on a variable list, a syntax error results.
• CLUSTER ignores unrecognized ROWTYPE_ values.
• When you are reading a matrix created with MATRIX DATA, you should supply a value
label for PROX of either SIMILARITY or DISSIMILARITY so the matrix is correctly identified.
If you do not supply a label, CLUSTER assumes DISSIMILARITY. (See “Format of
the Matrix Data File” below.)
• The program reads variable names, variable and value labels, and print and write formats
from the dictionary of the matrix data file.
• MATRIX=IN cannot be specified unless a working data file has already been defined. To
read an existing matrix data file at the beginning of a session, use GET to retrieve the
matrix file and then specify IN(*) on MATRIX.
• The variable list on CLUSTER can be omitted when a matrix data file is used as input. By
default, all cases or variables in the matrix data file are used in the analysis. Specify a variable
list when you want to read in a subset of items for analysis.
Format of the Matrix Data File
• The matrix data file can include three special variables created by the program:
ROWTYPE_, ID, and VARNAME_.
• Variable ROWTYPE_ is a string variable with value PROX (for proximity measure).
PROX is assigned value labels containing the distance measure used to create the matrix
and either SIMILARITY or DISSIMILARITY as an identifier. Variable VARNAME_ is a short
string variable whose values are the names of the new variables. Variable CASENO_ is a
numeric variable with values equal to the original case numbers.
• ID is included only when an identifying variable is not specified on the ID subcommand.
ID is a short string and takes the value CASE m, where m is the actual number of each
case. Note that m may not be consecutive if cases have been selected.
• If an identifying variable is specified on the ID subcommand, it takes the place of ID
between ROWTYPE_ and VARNAME_. Up to 20 characters can be displayed for the identifying
variable.