options ls=80 nodate pageno=1 NOFMTERR; 

 *  Class04_10.sas   20 Sept 2010;


  * proc print data=ph6470.child_iq (obs=5);

  ******************************;
  data a;
   input id color$ mass;
   cards;
   12 orange 3650
   13 blue  3877
   15 yellow 4103
   ;

 data b;
   input id mass pH;
   cards;
   13 11267 7.8
   14 3568 8.2
   15 4103 5.1
   ;
 data c;
   input id mss pH;
   cards;
   13 11267 7.8
   14 3568 8.2
   15 4103 5.1
   ;

 data d;
   merge a (in = in_a) b (in = in_b);
   by id;
   save_in_a = in_a;
   save_in_b = in_b;
   in_both = (in_a=1 AND in_b=1);

 proc print data=d;



************************************;

 data e;
   input id visit dbp;
   cards;
   101 1 77
   101 2 75
    .  3 80
   102 1 71
   102 2 74
   102 3 68
   ;

 data f;
   input id visit weight;
   cards;
   101 1 145
   101 2 149
   101 3 152
   102 1 181
   102 2 176
   ;

 proc sort data=E; by id visit;
 proc sort data=F; by id visit;

 data g;
   merge e f;
   by id;

 proc print data=g;

  data K;
   merge E F;
   by id visit;

 proc print data=K;

 data h;
   set f;
   by id;
   first_id = first.id;
   last_id = last.id;

 proc print data=h;

 data M; * count obs per ID;
   set F;
   by id;
   retain count;
   if (first.id = 1) then count=0;
   count = count + 1;
   if (last.id = 1) then output;
   

 proc print data=M;



  run; quit;