SPSS® 12.0 Command Syntax Reference

Domain Errors
Transformation Expressions 45
Domain errors occur when numeric expressions are mathematically undefined or cannot be
represented numerically on the computer for reasons other than missing data. Two common
examples are division by 0 and the square root of a negative number. When SPSS detects a
domain error, it issues a warning and assigns the system-missing value to the expression. For
example, the command COMPUTE TESTVAR = TRUNC(SQRT(X/Y) * .5) returns systemmissing
if X/Y is negative or if Y is 0.
The following are domain errors in numeric expressions:
** A negative number to a non-integer power.
/ A divisor of 0.
MOD A divisor of 0.
SQRT A negative argument.
EXP An argument that produces a result too large to be represented on the computer.
LG10 A negative or 0 argument.
LN A negative or 0 argument.
ARSIN An argument whose absolute value exceeds 1.
NORMAL A negative or 0 argument.
PROBIT A negative or 0 argument, or an argument 1 or greater.
String Expressions
Expressions involving string variables can be used on COMPUTE and IF commands and in
logical expressions on commands such as IF, DO IF, LOOP IF, and SELECT IF.
• A string expression can be a constant enclosed in apostrophes (for example, ‘IL’), a string
function (see “String Functions” below), or a string variable.
• An expression must return a string if the target variable is a string.
• The string returned by a string expression does not have to be the same length as the
target variable; no warning messages are issued if the lengths are not the same. If the
target variable produced by a COMPUTE command is shorter, the result is right-trimmed.
If the target variable is longer, the result is right-padded.
String Functions
• The target variable for each string function must be a string and must have already been
declared (see STRING).
• Multiple arguments in a list must be separated by commas.