Want all observations within a group (name AND ID) to be 1 if first obs within group is 1

[KPCklebspn]

Dataset looks like this -

Name  ID  flag1

AJ      1     1

AJ      1     .

AJ      1     .

AJ      2     .

AJ      2     .

How do I make dataset looks like this -

Name  ID  flag1  varWant

AJ      1     1         1

AJ      1     .          1

AJ      1     .          1

AJ      2     .          .

AJ      2     .          .

Thanks!

[KPCklebspn]

Dataset looks like this -

Name  ID  flag1

AJ      1     1

AJ      1     .

AJ      1     .

AJ      2     .

AJ      2     .

How do I make dataset looks like this -

Name  ID  flag1  varWant

AJ      1     1         1

AJ      1     .          1

AJ      1     .          1

AJ      2     .          .

AJ      2     .          .

Thanks!

[RW9]

data want;
  set have;
  retain varwant;
  by name id;
  if first.name and first.id then varwan1;
run;

[PaigeMiller · Accepted solution]

Try this — assumes data is sorted by name and id.

data want;
    set have;
    retain varWant;
    by name id;
    if first.id and flag1=1 then varWant=1;
    if first.id and flag1^=1 then varWant=.;
run;
    

[novinosrin]

data have;
input Name $ ID  flag1;
cards;
AJ      1     1
AJ      1     .
AJ      1     .
AJ      2     .
AJ      2     .
;

data want;
set have;
by id;
retain varWant;
if first.id then do;
call missing(varwant);
if flag1 then varWant=flag1;
end;
run;