I need a variable in my output populated with 'y' if variable result is last.result but gettng erro

[Aliya-begum]

data VS;
input ptid @5 vsdtc ddmmyy10. @17 result;
format vsdtc ddmmyy10.;
cards;
101 24/10/2018 110
101 25/10/2018 120
101 26/10/2018 115
101 27/10/2018 125
101 28/10/2018 135
102 23/10/2018 130
102 25/10/2018 120
102 26/10/2018 110
102 29/10/2018 115
102 30/10/2018 125
103 24/10/2018 120
103 26/10/2018 140
103 27/10/2018 110
103 28/10/2018 115
103 28/10/2018 145
;
run;

data DM;
input ptid @8 rfstdtc ddmmyy10.;
format rfstdtc ddmmyy10.;
cards;
101 26/10/2018
102 26/10/2018
103 27/10/2018
;
run;

proc sort data=VS;
by ptid;
run;
proc sort data=DM;
by ptid;
run;
data VS1;
merge VS DM;
by ptid;
run;
proc print;
run;

DATA VS2 VS3;
set VS1;
if vsdtc < rfstdtc then output VS2;
if vsdtc > rfstdtc then output VS3;
run;
DATA NEWL;
SET VS2;
IF LAST.result THEN vsblfl = 'Y';
RUN;
PROC PRINT;
RUN

[PeterClemmensen]

What is the error?

[Aliya-begum]

its showing variable last.result is uninitialized.

[error_prone]

If you want to use last(or first you have to use by, too. And I am wondering that you don't get a warning or at least a note saying exactly that.

[Aliya-begum]

ok

[RW9 · Accepted solution]

Please avoid coding in upper case, its shouting code.  Missing by line:

data newl; 
  set vs2;
  by result;
  if last.result then vsblfl='Y';
run;

[Aliya-begum]

sure ill...and thanks for the reply