SAS-如何从SAS宏返回值？

我想从我创建的SAS宏返回一个值，但我不确定如何返回。宏计算数据集中的观察数。我希望返回观察值的数量

%macro nobs(library_name, table_name);
  proc sql noprint;
    select nlobs into :nobs
    from dictionary.tables
    where libname = UPCASE(&library_name)
      and memname = UPCASE(&table_name);
  quit;

  *return nobs macro variable;
  &nobs
%mend;

%let num_of_observations = %nobs('work', 'patients');

---

此外，我希望宏中使用的

&nobs

宏变量是该宏的局部变量，而不是全局变量。如何才能做到这一点？

除非仅使用宏语句编写，否则无法从函数样式宏“返回”值。昆汀的链接提供了一个如何做到这一点的例子

例如，您不能使用这样的宏，因为PROC SQL不能在<代码> %PUT/<代码>语句的中间执行（这可能是其他更复杂的处理方法，例如：代码> DOUBUL，但不是您编写的方法）。 在没有重大更改的情况下，最好创建一个全局宏变量，并在后续语句中使用它

---

若要创建原始宏的本地宏变量，必须首先通过宏定义中的

%local

语句声明它。

SAS宏插入代码。它永远不会返回值，尽管在某些情况下可以模拟函数，通常需要类似的解决方法

%nobs(work, patients, toReturn=num_of_observations )

**为了帮助您理解发生了什么，我建议打印宏在日志中插入的代码：

options mprint;

我们将要填充的宏变量的名称传递给宏，我发现最实用的方法是

• 不要求我的宏的用户在库名和成员名周围加引号
• 使变量名成为命名的宏变量，这样我们就可以给它一个默认值
  %宏nobs（库名称、表名称、toReturn=nobs）

确保要返回的变量存在

• 如果它存在，则在该宏外部已知
• 否则，如果我们在这里创建它，默认情况下它将是本地的，当我们离开宏时它将丢失

  %if not %symexist(&toReturn.) %then %global &toReturn.;
  

在SQL中，I

• 使用SASHELP.VTABLE，SAS提供的元数据视图
• 添加我在宏调用中省略的引号（“，而不是“”：宏变量不在单个qoutes中替换）
• 使用宏%upcase函数代替SAS upcase函数，因为它有时会提高性能

  proc sql noprint;
      select nobs
      into :&toReturn.
      from sashelp.vtable
      where libname = %UPCASE("&library_name.")
      and memname = %UPCASE("&table_name.");
  quit;
  

  %修补

请注意，如果调用宏中的宏，请运行此代码并阅读日志以了解原因

%macro test_nobs();
    %nobs(sashelp, class); ** will return the results in nobs **;

    %nobs(sashelp, shoes, toReturn=num_of_shoes);

    %let num_of_cars = ;
    %nobs(sashelp, cars, toReturn=num_of_cars);

    %put NOTE: inside test_nobs, the following macro variables are known;
    %put _user_;
%mend;

%test_nobs;
%put NOTE: outside test_nobs, the following macro variables are known;
%put _user_;

---

编写宏这样的函数有什么问题？

i、 e.可以用作

%let myVar=%myMacro（myArgument）

• 您可以使用用户编写的宏，就像它是一个函数一样，如果您所做的只是
  • 调用一些类似宏函数的

    %doSomething（with someting）

  • 使用

    %let someVar=

    语句为宏变量赋值
  • “返回”您的结果，通常在

    %mend

• 一旦在宏中包含

  proc

  或

  data

  步骤，这将不再有效
• 幸运的是，%sysFunc（）起到了解救作用，因此我们可以使用任何数据步函数
• 这包括低级功能，如

  open

  、

  fetch

  和

  close

  ，它们甚至可以访问您的数据
• 书呆子们可以用它做很多事情，但即使你是书呆子，你的老板也很少给你时间这么做

我们如何解决这个问题？，即我应该使用哪些构建块来解决这个问题

• proc fcmp

  允许将一些数据步骤语句打包到子例程或函数中
• 此函数用于数据步骤，可在

  %sysfunc（）

• 在此函数中，您可以调用

  run\u macro

  立即在后台执行任何宏

现在我们准备好了实际的解决方案

步骤1：编写辅助宏

• 没有参数
• 使用一些全局宏变量
• 在全局宏变量中“返回”其结果

我知道这是一个不好的编码习惯，但为了降低风险，我们用前缀限定这些变量。应用于问题中的示例

** macro nobsHelper retrieves the number of observations in a dataset
    Uses global macro variables:
        nobsHelper_lib: the library in which the dataset resides, enclosed in quotes
        nobsHelper_mem: the name of the dataset, enclosed in quotes
    Writes global macro variable:
        nobsHelper_obs: the number of observations in the dataset 

    Take care nobsHelper exists before calling this macro, or it will be ost
**;
%macro nobsHelper();
    ** Make sure nobsHelper_obs is a global macro variable**;
    %global nobsHelper_obs;

    proc sql noprint;
        select nobs
        into :nobsHelper_obs
        from sashelp.vtable
        where libname = %UPCASE(&nobsHelper_lib)
          and memname = %UPCASE(&nobsHelper_mem);
    quit;
    %* uncomment these put statements to debug **;
    %*put NOTE: inside nobsHelper, the following macro variables are known;
    %*put _user_;
%mend;

步骤2：编写助手函数

**Functions need to be stored in a compilation library;
options cmplib=sasuser.funcs;

** function nobsHelper, retrieves the number of observations in a dataset
    Writes global macro variables:
        nobsHelper_lib: the library in which the dataset resides, enclosed in quotes
        nobsHelper_mem: the name of the dataset, enclosed in quotes
    Calls the macro nobsHelper

    Uses macro variable:
        nobsHelper_obs: the number of observations in the dataset 
**;
proc fcmp outlib=sasuser.funcs.trial;
    ** Define the function and specity it should be called with two character vriables **;
    function nobsHelper(nobsHelper_lib $, nobsHelper_mem $);
        ** Call the macro and pass the variables as global macro variables 
        ** The macro variables will be magically qouted **;
        rc = run_macro('nobsHelper', nobsHelper_lib, nobsHelper_mem);
        if rc then put 'ERROR: calling nobsHelper gave ' rc=;

        ** Retreive the result and pass it on **;
        return (symget('nobsHelper_obs'));
    endsub;
quit;

** macro nobs retrieves the number of observations in a dataset
    Parameters:
        library_name: the library in which the dataset resides
        member_name: the name of the dataset
    Inserts in your code:
        the number of observations in the dataset 
    Use as a function
**;
%macro nobs(library_name, member_name);
    %sysfunc(nobsHelper(&library_name, &member_name));

    %* Uncomment this to debug **;
    %*put _user_;
%mend;

%let num_carrs = %nobs(sasHelp, cars);
%put There are &num_carrs cars in sasHelp.Cars;

Data aboutClass;
    libname = 'SASHELP';
    memname = 'CLASS';
    numerOfStudents = %nobs(sasHelp, class);
run;

步骤3：编写一个方便的宏来使用帮助程序

**Functions need to be stored in a compilation library;
options cmplib=sasuser.funcs;

** function nobsHelper, retrieves the number of observations in a dataset
    Writes global macro variables:
        nobsHelper_lib: the library in which the dataset resides, enclosed in quotes
        nobsHelper_mem: the name of the dataset, enclosed in quotes
    Calls the macro nobsHelper

    Uses macro variable:
        nobsHelper_obs: the number of observations in the dataset 
**;
proc fcmp outlib=sasuser.funcs.trial;
    ** Define the function and specity it should be called with two character vriables **;
    function nobsHelper(nobsHelper_lib $, nobsHelper_mem $);
        ** Call the macro and pass the variables as global macro variables 
        ** The macro variables will be magically qouted **;
        rc = run_macro('nobsHelper', nobsHelper_lib, nobsHelper_mem);
        if rc then put 'ERROR: calling nobsHelper gave ' rc=;

        ** Retreive the result and pass it on **;
        return (symget('nobsHelper_obs'));
    endsub;
quit;

** macro nobs retrieves the number of observations in a dataset
    Parameters:
        library_name: the library in which the dataset resides
        member_name: the name of the dataset
    Inserts in your code:
        the number of observations in the dataset 
    Use as a function
**;
%macro nobs(library_name, member_name);
    %sysfunc(nobsHelper(&library_name, &member_name));

    %* Uncomment this to debug **;
    %*put _user_;
%mend;

%let num_carrs = %nobs(sasHelp, cars);
%put There are &num_carrs cars in sasHelp.Cars;

Data aboutClass;
    libname = 'SASHELP';
    memname = 'CLASS';
    numerOfStudents = %nobs(sasHelp, class);
run;

最后使用它

**Functions need to be stored in a compilation library;
options cmplib=sasuser.funcs;

** function nobsHelper, retrieves the number of observations in a dataset
    Writes global macro variables:
        nobsHelper_lib: the library in which the dataset resides, enclosed in quotes
        nobsHelper_mem: the name of the dataset, enclosed in quotes
    Calls the macro nobsHelper

    Uses macro variable:
        nobsHelper_obs: the number of observations in the dataset 
**;
proc fcmp outlib=sasuser.funcs.trial;
    ** Define the function and specity it should be called with two character vriables **;
    function nobsHelper(nobsHelper_lib $, nobsHelper_mem $);
        ** Call the macro and pass the variables as global macro variables 
        ** The macro variables will be magically qouted **;
        rc = run_macro('nobsHelper', nobsHelper_lib, nobsHelper_mem);
        if rc then put 'ERROR: calling nobsHelper gave ' rc=;

        ** Retreive the result and pass it on **;
        return (symget('nobsHelper_obs'));
    endsub;
quit;

** macro nobs retrieves the number of observations in a dataset
    Parameters:
        library_name: the library in which the dataset resides
        member_name: the name of the dataset
    Inserts in your code:
        the number of observations in the dataset 
    Use as a function
**;
%macro nobs(library_name, member_name);
    %sysfunc(nobsHelper(&library_name, &member_name));

    %* Uncomment this to debug **;
    %*put _user_;
%mend;

%let num_carrs = %nobs(sasHelp, cars);
%put There are &num_carrs cars in sasHelp.Cars;

Data aboutClass;
    libname = 'SASHELP';
    memname = 'CLASS';
    numerOfStudents = %nobs(sasHelp, class);
run;

我知道这很复杂但至少所有无聊的工作都完成了。 你可以在老板接受的时间内复制、粘贴和修改这些内容。

---

;

我将回答斑比在评论中提出的核心问题：

这里我主要关心的是如何从宏返回值

我要用一种重要的方式和德克争论。他说：

SAS宏插入代码。它永远不会返回值，尽管在某些情况下可以模拟函数

我不同意。SAS宏返回插入到处理流中的文本。回报绝对是一个合适的术语。当文本恰好是单个数字时，可以说它返回一个值

但是，如果宏除返回一个值外还包含宏语句，则该宏只能返回该值。也就是说，每一行都必须以

%

开头。任何不以

%

开头的内容都将被返回（一些以

%

开头的内容也可能被返回）

因此，重要的问题是，如何仅返回宏中的值

---

在某些情况下，如本例，完全可以只使用宏代码。事实上，在许多情况下，这在技术上是可能的——尽管在许多情况下，这比你应该做的工作要多

Jack Hamilton的链接中包含了一个适用于此的示例。他驳斥了这个例子

%global sum;

%macro get_something_back(input1, input2, outvar);
  %let &outvar = &sysevalf(&input1 + &input2);
%mend;

%get_something(1, 2, sum);