title: how to remove duplicates in SAS data step
body: <p>How to remove duplicates in SAS data step.  </p>
  
  <pre><code>data uscpi;
        input year month cpi;
     datalines;
     1990  6 129.9
     1990  7 130.4
     1990  8 131.6
     1990  9 132.7
     1991  4 135.2
     1991  5 135.6
     1991  6 136.0
     1991  7 136.2
     ;
     run;
  
  PROC SORT DATA = uscpi OUT = uscpi_dist NODUPKEY; 
   BY year ; 
   RUN; 
  </code></pre>
  
  <p>i can with proc step, but how to remove it in data step. Thanks in advance</p>