sasretain用法

sasretain用法

The basic syntax of RETAIN statement is as follows:

RETAIN …;

Where,

… are the variables

whose values have to be maintained through out the iteration of

the Data Step.

When the RETAIN statement is used, the value of the variable

will be maintained between the iterations until the variable is

modified with any arithmetic or character operation or until a

DROP or KEEP statement is encountered.

If the RETAIN statement is used and the OUTPUT statement is

used in the same DATA Step, then the output dataset will contain

observation for the variables other than the ones specified in

the RETAIN statement. For example, if the two variables x and y

are listed in the RETAIN statement, then the variables x and y

will be maintained from the previous iteration but the variables

other than x and y will be replaced from the current iteration.

Example 1:

Suppose we have the following dataset with four observations

and three variables

Data test1;

Input Var1 Var2 Var3;

Datalines;

1510

2720

3625

4930

Run;

Now if we want to add 10 to each observation of Var3 using a

DATA Step with a RETAIN statement, then the program will be as

follows

Data test2;

Set test1;

Retain Var3;

Var3 = Var3 + 10;

Run;

The resulting dataset will be as follows

Var1 Var2 Var3

1520

2730

3635

4940

Example 2:

Suppose we have the following dataset with four observations

and three variables

Data test3;

Input Var1 Var2 Var3;

Datalines;

1510

2720

3625

4930

Run;

Now we want to find the cumulative sum for each observation

in Var3. For this purpose, we will use a DATA Step with a RETAIN

statement.

Data test4;

Set test3;

Retain Var3;

Var3 = Var3 + Var3_old;

Run;

The resulting output dataset will be as follows

Var1 Var2 Var3

1510

2730

3655

4985

We can see that the value of Var3 in the second observation

is the sum of the Var3 values of the first and the second

observation and so on.

Example 3:

Suppose we have the following dataset with four observations

and three variables

Data test5;

Input Var1 Var2 Var3;

Datalines;

1510

27.

3625

4930

Run;

Now we want to assign the value of 10 to Var3 in the second

observation. For this purpose, we will use a DATA Step with a

RETAIN statement.

Data test6;

Set test5;

Retain Var3;

If Var3_old = . Then Var3 = 10;

Run;

The resulting output dataset will be as follows

Var1 Var2 Var3

1510

2710

3625

4930

We can see that the value of Var3 in the second observation

is assigned the value of 10. This is done using the RETAIN

statement.

From the above examples, we can clearly see that the SAS

RETAIN statement is used to maintain the current value of a

variable through multiple iterations of a DATA step. It is

mainly used when we have to manipulate the data like calculating

a cumulative sum or finding the difference between the values of

the same variable at different iteration or to assign a missing

value when the first non-missing observation of the variable is

encountered.