SAS 9.4 Language Reference, 6th Edition

Log 5.2 SAS Log Results for a Missing Value in a Statistic Function

143 data test;

144 x=.;

145 y=5;

146 a=x+y;

147 b=sum(x,y);

148 c=5;

149 c+x;

150 put a= b= c=;

151 run;

a=. b=5 c=5

NOTE: Missing values were generated as a result of performing an operation on

missing values.

Each place is given by: (Number of times) at (Line):(Column).

1 at 146:6

NOTE: The data set WORK.TEST has 1 observations and 5 variables.

NOTE: DATA statement used (Total process time):

real time 0.12 seconds

cpu time 0.01 seconds

Adding X and Y together in an expression produces a missing result because the value of

X is missing. The value of A, therefore, is missing. However, since the SUM function

ignores missing values, adding X to Y produces the value 5, not a missing value.

Note: The SUM statement also ignores missing values, so the value of C is also 5.

For more information about functions, see “SAS Functions and CALL Routines by

Category” in SAS Functions and CALL Routines: Reference.

Working with Missing Values

How to Represent Missing Values in Raw Data

The following table shows how to represent each type of missing value in raw data so

that SAS reads and stores the value appropriately.

Table 5.2 Representing Missing Values

Missing Values Representation in Data

Numeric

. (a single decimal point)

Character

' ' (a blank enclosed in quotation marks)

Special

.letter (a decimal point followed by a letter, for example, .B)

Special

._(a decimal point followed by an underscore)

Working with Missing Values 89

How to Set Variable Values to Missing in a DATA Step

You can set values to missing within your DATA step by using program statements such

as this one:

if age<0 then

age=.;

This statement sets the stored value of Age to a numeric missing value if Age has a value

less than 0.

Note: You can display a missing numeric value with a character other than a period by

using the DATA step's MISSING statement or the MISSING= system option.

The following example sets the stored value of Name to a missing character value if

Name has a value of “none”:

if name="none" then name='';

Alternatively, if you want to set to a missing value for one or more variable values, you

can use the CALL MISSING routine. For example:

call missing(sales, name);

This sets both variable values to a missing value.

Note: You can mix character and numeric variables in the CALL MISSING routine

argument list.

How to Check for Missing Values in a DATA Step

You can use the N and NMISS functions to return the number of nonmissing and

missing values, respectively, from a list of numeric arguments.

When you check for ordinary missing numeric values, you can use code that is similar to

the following:

if numvar=. then do;

If your data contains special missing values, you can check for either an ordinary or

special missing value with a statement that is similar to the following:

if numvar<=.z then do;

To check for a missing character value, you can use a statement that is similar to the

following:

if charvar=' ' then do;

The MISSING function enables you to check for either a character or numeric missing

value, as in:

if missing(var) then do;

In each case, SAS checks whether the value of the variable in the current observation

satisfies the condition specified. If it does, SAS executes the DO group.

Note: Missing values have a value of false when you use them with logical operators

such as AND or OR.

90 Chapter 5 • Missing Values