SPSS® 12.0 Command Syntax Reference

Syntax Rules
SELECT IF 1479
• Logical expressions can be simple logical variables or relations, or complex logical tests
involving variables, constants, functions, relational operators, and logical operators. The
logical expression can use any of the numeric or string functions allowed in COMPUTE
transformations (see COMPUTE and see “Transformation Expressions” on p. 37 in
Volume I).
• Parentheses can be used to enclose the logical expression. Parentheses can also be used
within the logical expression to specify the order of operations. Extra blanks or parentheses
can be used to make the expression easier to read.
• A relation can compare variables, constants, or more complicated arithmetic expressions.
Relations cannot be abbreviated. For example, (A EQ 2 OR A EQ 5) is valid while
(A EQ 2 OR 5) is not. Blanks (not commas) must be used to separate relational operators
from the expressions being compared.
• A relation cannot compare a string variable to a numeric value or variable, or vice versa.
A relation cannot compare the result of the logical functions SYSMIS, MISSING, ANY, or
RANGE to a number.
• String values used in expressions must be specified in quotation marks and must include
any leading or trailing blanks. Lowercase letters are considered distinct from uppercase
letters.
Operations
• SELECT IF permanently selects cases. Cases not selected are dropped from the working
data file.
• The logical expression is evaluated as true, false, or missing. If a logical expression is
true, the case is selected; if it is false or missing, the case is not selected.
• Multiple SELECT IF commands issued prior to a procedure command must all be true for
a case to be selected.
• SELECT IF should be placed before other transformations for efficiency considerations.
• Logical expressions are evaluated in the following order: first numeric functions, then exponentiation,
then arithmetic operators, then relational operators, and last logical operators.
Use parentheses to change the order of evaluation.
• If N OF CASES is used with SELECT IF, the program reads as many records as required to
build the specified n cases. It makes no difference whether the N OF CASES precedes or
follows the SELECT IF.
• System variable $CASENUM is the sequence number of a case in the working data file.
Although it is syntactically correct to use $CASENUM on SELECT IF, it does not produce
the expected results. To select a set of cases based on their sequence in a file, create your
own sequence variable with the transformation language prior to selecting (see the
example below).