retain previous missing visits

[sam369]

Hi all,

i would like to retain the previous values to the missing visits;

have:

visit	dt	SUBJID	testcd	testn		visitn	dy
WEEK0	07Dec2015	100	TEST	1		2	1
WEEK2	20Dec2015	100	TEST	1		4	14
WEEK4	03Jan2016	100	TEST	1		5	28
WEEK8	01Feb2016	100	TEST	1		6	57
FOLLOW-UP	07Feb2016	100	TEST	1		801	63

want:

visit	dt	SUBJID	testcd	testn		visitn	dy	flg
WEEK0	07Dec2015	100	TEST	1		2	1
WEEK0	07Dec2015	100	TEST	1		3	1	1
WEEK2	20Dec2015	100	TEST	1		4	14
WEEK4	03Jan2016	100	TEST	1		5	28
WEEK8	01Feb2016	100	TEST	1		6	57
WEEK8	01Feb2016	100	TEST	1		7	57	1
WEEK8	01Feb2016	100	TEST	1		8	57	1
WEEK8	01Feb2016	100	TEST	1		9	57	1
WEEK8	01Feb2016	100	TEST	1		10	57	1
FOLLOW-UP	07Feb2016	100	TEST	1		801	63

i tried:

data want;
  set have;
   by subjid testn test visitn dt;
  output;
   do visitn=2 to 10;
     flg=1;
     output;
   end;
run;

[ballardw]

For week8 how do we know that we are supposed to stop at visitn of 10? Is 10 going to be the stop for all Subjid?

Dare we ask why there is no visitn=1 in the example? What do we do if the first vistn value is greater than 2?

Will there be any WeekN visits after Follow-Up for a given Subid? If so you should provide an example of what the desired result might be.

[novinosrin]

data have;
input visit :$10. date :date7. subjid testcd $ testn visitn dy;
datalines;
WEEK0	7-Dec-15	100	TEST	1		2	1
WEEK2	20-Dec-15	100	TEST	1		4	14
WEEK4	3-Jan-16	100	TEST	1		5	28
WEEK8	1-Feb-16	100	TEST	1		6	57
FOLLOW-UP	7-Feb-16	100	TEST	1		801	63
;



data want;
set have;
retain _v _dy;
__v=visitn;
__dy=dy;
if _n_>1 and visit ne 'FOLLOW-UP' and visitn ne _v+1 then
do;
	do visitn=_v+1  to visitn-1;
	dy=_dy;
	flag=1;
	output;
	end;
end;
flag=.;
visitn=__v;
dy=__dy;
output;
_v=visitn;
_dy=dy;
drop _:;
run;

EDIT: Since i am a very lazy person, I didn;t bother retaining all variables in your input dataset. But if you follow the code , you can do so.  

[novinosrin · Accepted solution]

To handle by groups

data have;
input visit :$10. date :date7. subjid testcd $ testn visitn dy;
datalines;
WEEK0	7-Dec-15	100	TEST	1		2	1
WEEK2	20-Dec-15	100	TEST	1		4	14
WEEK4	3-Jan-16	100	TEST	1		5	28
WEEK8	1-Feb-16	100	TEST	1		6	57
FOLLOW-UP	7-Feb-16	100	TEST	1		801	63
;

data want;
do _n_= 1 by 1 until(last.subjid);
set have;
by subjid;
__v=visitn;
__dy=dy;
if _n_=1 then call missing(_v, _dy);
else if _n_>1 and visit ne 'FOLLOW-UP' and visitn ne _v+1 then
do;
	do visitn=_v+1  to visitn-1;
	dy=_dy;
	flag=1;
	output;
	end;
end;
flag=.;
visitn=__v;
dy=__dy;
output;
_v=visitn;
_dy=dy;
end;
drop _:;
run;

[sam369]

Thank you all!!!