为什么我的 %DO %UNTIL 循环在 SAS 宏程序中条件未满足的情况下仍然执行？

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英文:

Why is my %DO %UNTIL loop implemented even though the loop not satisfied the conditions in SAS MACRO PROGRAM?

问题

这是您的SAS宏程序代码的翻译部分：

  1. %MACRO RegRepeat ; 
  3.     %global maxVIFvar ;      /* maxVIFvar: 全局符号表 */ 
  4. 	%global maxVIFval ;      /* maxVIFval: 全局符号表 */ 
  5. 	%global j ;              /*     j    : 全局符号表 */ 
  6. 	%let maxVIFval = 10000 ;  
  7. 	%let j = 1 ;             
  8. 	
  9. 	%do %WHILE(  &maxVIFval > 1000  ) ; 
  10. 	   
  11. 	    /* 下面是回归过程 */
  12. 	    PROC REG DATA=KNHANES.HNAP1319 ; 
  13. 		    TITLE ; 
  14. 		    TITLE "最大VIF值：&maxVIFval / 重复次数：&j" ; 
  15. 			WEIGHT wt_pft_pool ; 
  16. 			WHERE HE_COPD = 3 ; 
  17. 			MODEL HE_fev1_new = SEX_new AGE OBE INCM_LH DJ4_dg_new sm1_former sm1_current at_risk_occp
  18. 			                    &airPollution / 缺乏拟合 ADJRSQ VIF  ; 
  19. 			ods output ParameterEstimates = PE ;
  20. 		RUN ; 
  21. 		
  22. 		/* 下面是SQL过程 */
  23. 		PROC SQL ;
  24. 		    CREATE TABLE WORK.maxVIF AS
  25. 		    SELECT Variable, max(VarianceInflation) AS maxVIF
  26. 		    FROM WORK.PE
  27. 		    HAVING VarianceInflation = MAX(VarianceInflation) ; 
  28. 		QUIT ;
  29. 	
  30. 	    /* 下面是DATA步骤 */
  31. 		DATA WORK.maxVIFtoMV ;
  32. 			SET WORK.maxVIF ; 
  33. 			CALL SYMPUT("maxVIFvar", VARIABLE); 
  34. 			CALL SYMPUT("maxVIFval", maxVIF); 
  35. 		RUN ; 
  36. 		
  37. 		%let airPollution = %sysfunc(tranwrd(&airPollution, &maxVIFvar, )) ;
  38. 	    %let j = %eval(&j+1) ;     
  39. 		%PUT 最大VIF值：&maxVIFval / 重复次数：&j ; 
  40.    
  41. 	%end ;
  42. 	
  43. %MEND ;
  45. %RegRepeat

希望这能帮助您理解您的SAS宏程序代码。

英文:

I wrote the following SAS macro program code.

The purpose of the code is to repeat PROCREG while the condition(&maxVIFval > 1000) is satisfied.

However the %DO %WHILE loop is executed continually even though &maxVIFval has a value of 1000 or less.

I wonder what the reason is.

I'm looking for help..

Forgive my poor English.

  1. %MACRO RegRepeat ; 
  3.     %global maxVIFvar ;      /* maxVIFvar: global symbol table */ 
  4. 	%global maxVIFval ;      /* maxVIFval: global symbol table */ 
  5. 	%global j ;              /*     j    : global symbol table */ 
  6. 	%let maxVIFval = 10000 ;  
  7. 	%let j = 1 ;             
  8. 	
  9. 	%do %WHILE(  &maxVIFval > 1000  ) ; 
  10. 	   
  11. 	    /* Regression procedure below */
  12. 	    PROC REG DATA=KNHANES.HNAP1319 ; 
  13. 		    TITLE ; 
  14. 		    TITLE "MAX VIF: &maxVIFval / Repeated Number: &j" ; 
  15. 			WEIGHT wt_pft_pool ; 
  16. 			WHERE HE_COPD = 3 ; 
  17. 			MODEL HE_fev1_new = SEX_new AGE OBE INCM_LH DJ4_dg_new sm1_former sm1_current at_risk_occp
  18. 			                    &airPollution / lackfit ADJRSQ VIF  ; 
  19. 			ods output ParameterEstimates = PE ;
  20. 		RUN ; 
  21. 		
  22. 		/* SQL procedure below */
  23. 		PROC SQL ;
  24. 		    CREATE TABLE WORK.maxVIF AS
  25. 		    SELECT Variable, max(VarianceInflation) AS maxVIF
  26. 		    FROM WORK.PE
  27. 		    HAVING VarianceInflation = MAX(VarianceInflation) ; 
  28. 		QUIT ;
  29. 	
  30. 	    /* DATA Step below */
  31. 		DATA WORK.maxVIFtoMV ;
  32. 			SET WORK.maxVIF ; 
  33. 			CALL SYMPUT("maxVIFvar", VARIABLE); 
  34. 			CALL SYMPUT("maxVIFval", maxVIF); 
  35. 		RUN ; 
  36. 		
  37. 		%let airPollution = %sysfunc(tranwrd(&airPollution, &maxVIFvar, )) ;
  38. 	    %let j = %eval(&j+1) ;     
  39. 		%PUT MAX VIF: &maxVIFval / Repeated Number: &j ; 
  40.    
  41. 	%end ;
  42. 	
  43. %MEND ;
  45. %RegRepeat

These are sentences from the log window.

MPRINT(REGREPEAT): TITLE "MAX VIF: 10000 / Repeated Number: 1" ;

MPRINT(REGREPEAT): TITLE "MAX VIF: 1588.907368 / Repeated Number: 2" ;

MPRINT(REGREPEAT): TITLE "MAX VIF: 1297.8441436 / Repeated Number: 3" ;

MPRINT(REGREPEAT): TITLE "MAX VIF: 696.59402283 / Repeated Number: 4" ;

MPRINT(REGREPEAT): TITLE "MAX VIF: 569.83744288 / Repeated Number: 5" ;

Please let me know if you need any additional information.

Thank you for your kindness.

答案1

得分: 2

为了解决这个问题，使用%sysevalf(&maxVIFval > 1000)代替&maxVIFval > 1000。

当SAS在宏中比较两个数字时，当数字包含小数点和不包含小数点时，SAS有不同的规则。当存在小数点时，SAS将宏中的数字视为字符：

  1. %if 696.59402283>1000 %then %do;
  2.   %put 0;
  3. %end;
  4. %else %do;
  5.   %put 1;
  6. %end;
  8. 0

SAS在比较字符时，从左到右逐个字符进行比较，“6”在ASCII码序列中大于“1”，因此我们有 696.59402283>1000。

当没有小数点时，SAS将宏中的数字视为数字：

  1. %if 696>1000 %then %do;
  2.   %put 0;
  3. %end;
  4. %else %do;
  5.   %put 1;
  6. %end;
  8. 1

比较是基于数学规则进行的。

我建议您在宏中进行数字比较时始终使用%sysevalf()函数，除非您百分之百确定没有小数点。

英文:

To fix this issue, use %sysevalf(&maxVIFval > 1000) to instead of &maxVIFval > 1000.

When SAS compares two numbers in macro, it has different rules when numbers contain decimal point or not. When there is a decimal point, SAS treats numbers in macro as characters:

  1. %if 696.59402283>1000 %then %do;
  2.   %put 0;
  3. %end;
  4. %else %do;
  5.   %put 1;
  6. %end;
  8. 0

SAS compares characters char by char from left to right when comparing characters, "6" is larger than "1" in ascii code sequence, so we have 696.59402283>1000.

When there are no decimal points, SAS treats numbers in macro as numbers:

  1. %if 696>1000 %then %do;
  2.   %put 0;
  3. %end;
  4. %else %do;
  5.   %put 1;
  6. %end;
  8. 1

The comparsion is based on mathmatical rules.

I sugguest you always use %sysevalf() function if you want to do number comparsion in macro, unless you are 100% sure there are no decimal points.

huangapple
  • 本文由 发表于 2023年2月14日 09:31:32
  • 转载请务必保留本文链接：https://go.coder-hub.com/75442702.html
  • macros
  • sas
  • sas-macro
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