find first id and date

[hk2013]

data one;
input ID   Date total predicted;
cards;
1              6/24/18    200    250
1             6/30/18    200    270
1              6/18/20    200   230 
2               5/24/18     160   200
2             5/27/18     160   210
2             5/22/18     160   170
3          5/20/18     300   450
3           5/14/18     300   400
3            5/4/18     300     425
;

i want to pick the first date for each ID and subtract that date and IDs Predicted  from Total 

[PaigeMiller]

Show us the desired result. 

[hk2013]

result would look like this 
ID             Date       total  Predicted   diff
1              6/18/20    200    230           -30
2             5/22/18     160   170            -10
3            5/4/18     300     425           -125

[Reeza]

The way your data is sorted you're looking for the last. Is your data sort important and verified or do you need to verify it?

proc sort data=have; 
by id date;
run;

data want;
set have;
by id;
if first.id;
dif = predicted-total;
run;

Documentation references:

http://documentation.sas.com/?docsetId=lrcon&docsetTarget=n138da4gme3zb7n1nifpfhqv7clq.htm&docsetVer...

They have some good pictures that illustrate how BY groups work in the documentation. 

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@hk2013 wrote:

data one;
input ID   Date total predicted;
cards;
1              6/24/18    200    250
1             6/30/18    200    270
1              6/18/20    200   230 
2               5/24/18     160   200
2             5/27/18     160   210
2             5/22/18     160   170
3          5/20/18     300   450
3           5/14/18     300   400
3            5/4/18     300     425
;

i want to pick the first date for each ID and subtract that date and IDs Predicted  from Total 

---

[jebjur]

This code should give you the results you want:

data two (drop=temp);
set one;
 by ID;
 retain temp;
   if first.id then temp=total;
   else if last.id then do;
      diff=temp-predicted;
      output;
  end;
run;