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Chapter 4 Program Design of Data StepZhang YuhuaInstitute of Biomedical Engineering Building 8, 3rd floor, east sideTel:mail: zhangyh@sdu.edu.cnMain TopicsLoop programming DO – END statementBranch programming IF – THEN/ELSE statementChapter 4Loop programmingLoop: In the one processing of DATA step, some statements need to be run many times repeatedly. DO – END statement:Syntax: DO I = A to B by C; < Loop Body >; END;Description:The index variable (I) starts with the start value (A), then is incremented by the increment value (C) each time (I=I+C). The iterations continue as long as the index variable is less than or equal to the stop value (B). If a negative increment is used, then the rules reverse so that the index variable decrements to a lower bound. Note that the start, stop, and increment expressions are evaluated only once before the looping starts.Chapter 4Example 1: repeat 10 timesData a; do i=0 to 9; put i; * PUT: display the value of ‘i’ in LOG window. end;run;Note: If start value (A) and stop value (B)were omitted, the loop executed only once from DO to END. If ‘by C’ was omitted, C=1.Chapter 4Nested Loop: Example 2: Printing the multiplication tableData a; Do I = 1 to 9; * Multiplicand loops from 1 to 9; Do j = 1 to I; * Multiplier loops from 1 to 9; S = I * j; Put I “*” j “=“ S “ “ @@;* @@: No newline output; End ; Put;* Newline output; End;Run;Chapter 4编号高剂量低剂量对照组15.6-0.612.429.55.70.936.012.87.048.74.13.959.2-1.81.665.0-0.16.473.56.33.085.812.73.998.09.82.21015.512.61.11111.82.02.71216.35.67.81311.87.06.91414.67.91.5154.94.39.4168.16.43.8Prepare data for ANOVA:Example: To study the efficacy of different doses of a hypoglycemic drug, the decrease values (mmol/L) of 2-hour postprandial blood glucose were measured after 4 weeks of treatment in patients with type II diabetes, as shown in the table.Chapter 4Data a;Do i=1 to 16; Do j=1 to 3; Input x @@; Output; * Output: Write the data into dataset one-by-one; End;End;Cards;5.6 -0.