SPSS® 12.0 Command Syntax Reference

CLUSTER 229
• The variable list is required except when matrix input is used. It must be specified before
the optional subcommands.
• If matrix input is used, the variable list can be omitted. The names for the items in the matrix
are used to compute similarities or distances.
• You can specify a variable list to override the names for the items in the matrix. This
allows you to read in a subset of cases for analysis. Specifying a variable that does not
exist in the matrix results in an error.
MEASURE Subcommand
MEASURE specifies the distance or similarity measure used to cluster cases.
• If the MEASURE subcommand is omitted or included without specifications, squared
Euclidean distances are used.
• Only one measure can be specified.
Measures for Interval Data
For interval data, use any one of the following keywords on MEASURE:
SEUCLID Squared Euclidean distance. The distance between two items, x and y, is the
sum of the squared differences between the values for the items. SEUCLID is
the measure commonly used with centroid, median, and Ward’s methods of
clustering. SEUCLID is the default and can also be requested with keyword
DEFAULT.
SEUCLID( xy , ) Σi( xi – yi) 2
=
EUCLID Euclidean distance. This is the default specification for MEASURE. The distance
between two items, x and y, is the square root of the sum of the squared
differences between the values for the items.
EUCLID( x, y)
Σi( xi – yi) 2
=
CORRELATION Correlation between vectors of values. This is a pattern similarity measure.
CORRELATION( xy , )
Σi( ZxiZyi) = -------------------------
N – 1
where Z xi is the Z-score (standardized) value of x for the ith case or variable,
and N is the number of cases or variables.
COSINE Cosine of vectors of values. This is a pattern similarity measure.
COSINE( x, y)
Σi( xiy i)
=
----------------------------------
( Σix 2
i ) ( Σiy2 i )