In many situations the data available for analysis is incomplete and a placeholder must be used in place of a value to indicate that the value is unknown. One way that missing values are represented is through the $SYSMIS variable (see Variables Automatically Defined by PSPP). Another, more flexible way is through user-missing values which are determined on a per variable basis.
MISSING VALUES command sets user-missing values for variables.
MISSING VALUES var_list (missing_values). where missing_values takes one of the following forms: num1 num1, num2 num1, num2, num3 num1 THRU num2 num1 THRU num2, num3 string1 string1, string2 string1, string2, string3 As part of a range,
LOWESTmay take the place of num1;
HIGHESTmay take the place of num2.
MISSING VALUES sets user-missing values for numeric and string
variables. Long string variables may have missing values, but
characters after the first 8 bytes of the missing value must be
Specify a list of variables, followed by a list of their user-missing
values in parentheses. Up to three discrete values may be given, or,
for numeric variables only, a range of values optionally accompanied by
a single discrete value. Ranges may be open-ended on one end, indicated
through the use of the
MISSING VALUES command takes effect immediately. It is not
affected by conditional and looping constructs such as
DO IF or