Examples: DO Loops

Detailed functional analysis of DO loops. DO loops are flow control structures used to repeatedly execute a group of statements. They can be iterative (with an index, a list, or a sequence), or conditional (as long as a condition is true or until a condition becomes true). The presented examples cover these different forms, demonstrating their application for data manipulation, interest calculation, and other scenarios. It is emphasized that the syntax and behavior are identical whether the DATA step runs on the SAS^© compute server or in the CAS environment, although execution in CAS may sometimes occur in a single thread if no input table is specified.

Data Analysis

Type : CREATION_INTERNE

Examples use generated data (datalines) or SASHELP.

1 Code Block

DATA STEP Data

Explanation :
This example uses an iterative DO statement to repeatedly decrement the values of the 'balance' variable and write these values to the output dataset. The DATA step executes on the SAS compute server.

Copied!

1	DATA loan;
2	balance=10000;
3	DO payment_number=1 to 10;
4	balance=balance-1000;
5	OUTPUT;
6	END;
7	RUN;
8	PROC PRINT DATA=loan;
9	RUN;

2 Code Block

DATA STEP Data

Explanation :
This example uses the same iterative DO loop to execute the DATA step in CAS and create a CAS output table. Although the DATA step executes in CAS, it runs in a single thread because no input table is specified.

Copied!

1	cas casauto sessopts=(caslib='casuser');
2	LIBNAME mylib cas;
3
4	DATA mylib.loan;
5	balance=10000;
6	DO payment_number=1 to 10;
7	balance=balance-1000;
8	OUTPUT;
9	END;
10	RUN;
11	PROC PRINT DATA=mylib.loan;
12	RUN;

3 Code Block

DATA STEP Data

Explanation :
This example shows how to nest a DO loop within another to calculate the value of a one-year investment with an annual interest rate of 7.5%, compounded monthly. Nesting is useful when you need to repeat an internal action for each pass of the outer loop.

Copied!

1	DATA earn;
2	Capital=2000;
3	DO Year=1 to 10;
4	DO Month=1 to 12;
5	Interest=Capital*(.075/12);
6	Capital+Interest;
7	OUTPUT;
8	END;
9	END;
10	RUN;
11	PROC PRINT DATA=earn; RUN;

4 Code Block

DATA STEP Data

Explanation :
This example uses DOLIST syntax to iterate over a list of values, expressions, or sequences. The DO loop index successively takes the values specified in the list, which are separated by commas.

Copied!

1	DATA do_list;
2	x=-5;
3	DO i=5, /a single value/
4	5, 4, /multiple values/
5	x + 10, /an expression/
6	80 to 90 BY 5, /a sequence/
7	60 to 40 BY x; /a sequence with a variable/
8	OUTPUT;
9	END;
10	RUN;
11	PROC PRINT DATA=do_list; RUN;

5 Code Block

DATA STEP Data

Explanation :
This example uses the iterative DO TO-<value> syntax to repeatedly increment the values of 'x'. The OUTPUT statement is used to write each incremented value of 'x' to the output dataset. The 'TO' value specifies the final value of the index variable.

Copied!

1	DATA do_to;
2	x=0;
3	DO i=0 to 10;
4	x=x+1;
5	OUTPUT;
6	END;
7	RUN;
8	PROC PRINT DATA=do_to;
9	RUN;

6 Code Block

DATA STEP Data

Explanation :
This example uses the iterative DO TO-<value> BY-<increment> syntax to repeatedly increment the values of 'x'. The 'BY-<increment>' value specifies that the index variable is incremented by '2' with each execution of the loop. The OUTPUT statement writes each incremented value of 'x' to the output dataset.

Copied!

1	DATA do_to_by;
2	x=0;
3	DO i=0 to 10 BY 2;
4	x=x+1;
5	OUTPUT;
6	END;
7	RUN;
8	PROC PRINT DATA=do_to_by;
9	RUN;

7 Code Block

DATA STEP Data

Explanation :
This first DATA step uses a DO loop to repeatedly execute a group of statements as long as a condition is true. The program calculates the number of payments required for a specified loan amount by repeatedly decrementing the 'Balance' as long as the balance is greater than zero. The DATA step executes on the SAS compute server.

Copied!

1	DATA loan;
2	balance=10000;
3	payment=0;
4	DO while (balance>0);
5	balance=balance-1000;
6	payment=payment+1;
7	OUTPUT;
8	END;
9	RUN;
10	PROC PRINT DATA=mylib.loan;
11	RUN;

8 Code Block

DATA STEP Data

Explanation :
This DATA step loads the same data into a new table in a different library, 'mylib.loan', and then calculates the number of payments required for the specified loan. It does this by repeatedly iterating and decrementing the 'Balance' values until the balance is zero. The DATA step executes in CAS but in a single thread because there is no input table.

Copied!

1	LIBNAME mylib cas;
2
3	DATA mylib.loan;
4	balance=10000;
5	payment=0;
6	DO until (balance=0);
7	balance=balance-1000;
8	payment=payment+1;
9	OUTPUT;
10	END;
11	RUN;
12	PROC PRINT DATA=mylib.loan;
13	RUN;

This material is provided "as is" by We Are Cas. There are no warranties, expressed or implied, as to merchantability or fitness for a particular purpose regarding the materials or code contained herein. We Are Cas is not responsible for errors in this material as it now exists or will exist, nor does We Are Cas provide technical support for it.

Retour à la liste