SPSS® 12.0 Command Syntax Reference

926 MATRIX—END MATRIX
COMPUTE Statement
The COMPUTE statement carries out most of the calculations in the matrix program. It closely
resembles the COMPUTE command in the SPSS transformation language.
• The basic specification is the target variable, an equals sign, and the assignment expression.
Values of the target variable are calculated according to the specification on the assignment
expression.
• The target variable must be named first, and the equals sign is required. Only one target variable
is allowed per COMPUTE statement.
• Expressions that extract portions of a matrix, such as M(1,:) or M(1:3,4), are allowed to
assign values. (See “Matrix Notation Shorthand” on p. 918.) The target variable must be
specified as a variable.
• Matrix functions must specify at least one argument enclosed in parentheses. If an expression
has two or more arguments, each argument must be separated by a comma. For a
complete discussion of the functions and their arguments, see “Matrix Functions” on p. 927.
String Values on COMPUTE Statements
Matrix variables, unlike those in the SPSS transformation language, are not checked for data
type (numeric or string) when you use them in a COMPUTE statement.
• Numerical calculations with matrices containing string values will produce meaningless
results.
• One or more elements of a matrix can be set equal to string constants by enclosing the string
constants in apostrophes or quotation marks on a COMPUTE statement.
• String values can be copied from one matrix to another with the COMPUTE statement.
• There is no way to display a matrix that contains both numeric and string values, if you
compute one for some reason.
Example
COMPUTE LABELS={"Observe", "Predict", "Error"}.
PRINT LABELS /FORMAT=A7.
• LABELS is a row vector containing three string values.
Arithmetic Operations and Comparisons
The expression on a COMPUTE statement can be formed from matrix constants and variables,
combined with the arithmetic, relational, and logical operators discussed above. Matrix constructions
and matrix functions are also allowed.
Examples
COMPUTE PI = 3.14159265.
COMPUTE RSQ = R * R.
COMPUTE FLAGS = EIGENVAL >= 1.
COMPUTE ESTIM = {OBS, PRED, ERR}.