運用 Do loop 整理資料

• /*
  DO index-variable=start TO stop BY increment;
  SAS statements
  END;
  */
  • data test;
    Amount=1000;
    Rate=.075/12;
    do month=1 to 12; /*開始 Iteration */
        Earned+(amount+earned)*rate;
    end;  /*month 跑到 13 才停，因此最後是 13 */
    run;  /*輸出 所有變項值*/
  • do i=1 to Years;
    變項也可以當成 Stop 的依據
  • /*Decrementing DO Loops ，最後到 1 結束*/
  • a Series of Items
    • DO index-variable=
      2,5,9,13,27;
    • DO index-variable=
      'MON','TUE','WED','THR','FRI';
    • DO index-variable=
      Spring, Summer, Fall , Winter;  變項值

/*Nesting DO Loops*/

• data work.earn;
  do year=1 to 20; /*每年增資*/
      Capital+2000;
      do month=1 to 12; /*每月複利*/
          Interest=capital*(.012/12);
          capital+interest;
      end;
  end;
  run;

/*Conditionally Executing DO Loops*/

• /* DO UNTIL(expression); */
  在程式底才判斷，因此statement一定至少執行一次
  • data invest;
        do until (Capital>=9000);
            capital+1000;
            capital+capital*.10;
            Year+1;
            output;
        end;
    run;
    proc print noobs;run;
  • data invest;
        do Year=1 to 10  until (Capital>=20000);
            capital+1000;
            capital+capital*.10;
            output;
        end;
    if year=11 then year=10;
    /*index-variable 跑足就會多 1  */
    run;
    proc print noobs;run;
  • data invest;         /*依 condition 提早結束*/
        do Year=1 to 10  until (Capital>=20000);
            capital+5000;
            capital+capital*.10;
            output;
        end;
        if year=11 then year=10;
    run;
    proc print noobs;run;
• /* DO WHILE(expression); */
  在程式初就判斷，因此statement可能完全不執行
  • data invest;
        do while (Capital>=9000);
    *不會執行，因為初始是 0 ，要 >= 9000 才會動;
            capital+1000;
            capital+capital*.10;
            Year+1;
            output;
        end;
    run;

系統抽樣 搭配 Point-Output-Stop

• DATA TT;
      Do sample=1 to 206 by 5 ;
          SET SASUSER.frequentflyers  point=sample;
          Output;
      End;
                  Stop;
  RUN;