SPSS® 12.0 Command Syntax Reference

and
COMPUTE lagvar=LAG(var1).
EXECUTE.
COMPUTE var1=var1*2.
Transformation Expressions 53
yield very different results for the value of lagvar, since the former uses the transformed value
of var1 while the latter uses the original value.
Missing-Value Functions
• Each argument to a missing-value function (expression, variable name, or constant) must
be separated by a comma.
• Only numeric values can be used as arguments in missing-value functions.
• The keyword TO can be used to refer to a set of variables in the argument list for functions
NMISS and NVALID.
• The functions MISSING and SYSMIS are logical functions and can be useful shortcuts to
more complicated specifications on the IF, DO IF, and other conditional commands.
VALUE(arg) Ignore user-defined missing values. The value is treated as is. The
argument must be a variable name.
MISSING(arg) True or 1 if the value is user-missing or system-missing; false or 0
otherwise.
SYSMIS(arg) True or 1 if the value is system-missing; false or 0 otherwise.
NMISS(arg list) Number of system-missing values in the argument list.
NVALID(arg list) Number of valid values in the argument list.
Treatment of Missing Values in Arguments
If the logic of an expression is indeterminate because of missing values, the expression
returns a missing value, and the command is not executed. Table 6 summarizes how missing
values are handled in arguments to various functions.
Table 6 Missing values in arguments
Function Returns system-missing if
MOD (x1,x2) x1 is missing, or x2 is missing and x1 is not 0
MAX.n (x1,x2,...xk) fewer than n arguments are valid; the default n is 1
MEAN.n (x1,x2,...xk)
MIN.n (x1,x2,...x1)
SUM.n (x1,x2,...xk)