Retaining variable from previous observation when variable is missing in current observation

[Ksharp]

I know what is going on .

data have;
input TOTAL_NOTE_BALANCE_15YR ;
cards;
45746
43473
.
.
.
43011
;
run;

data want;
 do until(not missing(TOTAL_NOTE_BALANCE_15YR ) or last1);
   set have end=last1;
 end; 
   NEW_TOTAL_NOTE_BALANCE_15YR =TOTAL_NOTE_BALANCE_15YR ;
 do until(not missing(TOTAL_NOTE_BALANCE_15YR ) or last2);
   set have end=last2; 
   output;
 end;
run;

[SAS_inquisitive]

Hi Xia, How two DoW-loop is working here? Can you explain little bit? Thanks !

[Ksharp]

When _n_ eq 1 :

  the first do until will rolling here

45746 <---
43473
.
.
.
43011
;

assign 45746 to new variable.

the second do until will output this obs , so new variable retain 45746 and export to WANT dataset.

When _n_ eq 2 :

  the first do until will rolling here

45746 
43473 <---
.
.
.
43011
;

assign 43473  to new variable.

the second  do until will output this obs , so new variable retain 43473 and export to WANT dataset.

When _n_ eq 3 :

  the first do until will rolling here

45746 
43473 
.
.
.
43011 <---
;

assign 43011 to new variable.

the second  do until will output the following 4 obs utill 43011 , so new variable retain 43011 and export to WANT dataset with  these four obs .

etc...........

[SAS_inquisitive]

Thanks, Xia.  So it is kind of nested DoW loop?

[Ksharp]

Yes. It is DOW skill has been mentioned by many people and many times.