title: About SAS macro——how to use abs()/std()
body: <p>I write a macro sentence in SAS :</p>
  
  <pre><code>%macro loop;
  %let sigmav=0.1;
  .....
  %let sigmav_new=std(V);
  %if abs(%eval(&amp;sigmav-&amp;sigmav_new))&lt;0.001 %then %do;
  ......
  %mend;
  </code></pre>
  
  <p>But there are always errors of abs( ) and std( ). So I wonder whether there are special rules to express the function of abs() and std() in a macro. Hope for your help!</p>