Missing values in numeric expressions

Most numeric expressions receive the system-missing value when any one of the values in the expression is missing. Some arithmetic operations involving 0 can be evaluated even when the variables have missing values. These operations are:

• 0 * missing = 0
• 0 / missing = 0
• MOD(0, missing) = 0

  The .n suffix can be used with the statistical functions SUM, MEAN, MIN, MAX, SD, VARIANCE, and CFVAR to specify the number of valid arguments that you consider acceptable. The default of n is 2 for SD, VARIANCE, and CFVAR, and 1 for other statistical functions. For example,

  COMPUTE FACTOR = SUM.2(SCORE1 TO SCORE3). 

  computes the variable FACTOR only if a case has valid information for at least two scores. FACTOR is assigned the system-missing value if a case has valid values for fewer than two scores. If the number specified exceeds the number of arguments in the function, the result is system-missing.