Keeping only the observations you want

There are several ways you can let SAS know exactly which observations you want written to a data set. The first example below uses the subsetting IF statement. The second example accomplishes the same thing with the DELETE statement.

The subsetting IF statement

• IF condition;
  • if condition is true, continue to execute data step
  • if condition is false, stop processing current observation and return to top of data step
  • in particular, if condition is false do not output the current observation being formed in the PDV

     
      Example--only two observations will be output by the data step:
    
                   data alpha;
                        infile cards;
                        input a b c;
                        d=c-b;
                        if d>0;  /*output obs only if d>0 */
                   cards;
                   1 5 10
                   0 8 7
                   1 4 6
                   ;
                   run;
    
                   proc print; 
                   run;
    
     Proc print above would display the data set alpha like this:                                          
    
                  OBS  A   B   C   D
                  1    1   5   10  5
                  2    1   4   6   2
    

The DELETE statement

• IF condition THEN DELETE;
  • if condition is true, stop processing current observation and return to top of data step
  • in particular, if condition is true, do not output the current observation being formed in the PDV

     
      Example--this data step gives the same result as the data step above:
    
                   data alpha;
                        infile cards;
                        input a b c;
                        d=c-b;
                        if d<=0 then delete; /*do not output obs if d<=0*/ 
                   cards;
                   1 5 10
                   0 8 7
                   1 4 6
                   ;
                   run;
    
    

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Questions or comments?  If you are affiliated with the Carolina Population Center, send them to Phil Bardsley.