SAS 9.4 Language Reference, 6th Edition

For example, the numeric missing value (.) is sorted before the special numeric missing

value .A, and both are sorted before the special missing value .Z. SAS does not

distinguish between lowercase and uppercase letters when sorting special numeric

missing values.

Note: The numeric missing value sort order is the same regardless of whether your

system uses the ASCII or EBCDIC collating sequence.

Character Variables

Missing values of character variables are smaller than any printable character value.

Therefore, when you sort a data set by a character variable, observations with missing

(blank) values of the BY variable always appear before observations in which values of

the BY variable contain only printable characters. However, some usually unprintable

characters (for example, machine carriage-control characters and real or binary numeric

data that have been read in error as character data) have values less than the blank.

Therefore, when your data includes unprintable characters, missing values might not

appear first in a sorted data set.

When Variable Values Are Automatically Set to

Missing by SAS

When Reading Raw Data

At the beginning of each iteration of the DATA step, SAS sets the value of each variable

that you create in the DATA step to missing, with the following exceptions:

• variables named in a RETAIN statement

• variables created in a SUM statement

• data elements in a _TEMPORARY_ array

• variables created with options in the FILE or INFILE statements

• variables created by the FGET function

• data elements that are initialized in an ARRAY statement

• automatic variables

SAS replaces the missing values as it encounters values that you assign to the variables.

Thus, if you use program statements to create new variables, their values in each

observation are missing until you assign the values in an assignment statement, as shown

in the following DATA step:

data new;

input x;

if x=1 then y=2;

datalines;

4

1

3

1

;

86 Chapter 5 • Missing Values