help with retain statement

[knveraraju91]

Dear,

I created a data set 'two' which is similar to what i am working. I need help in data three. The retain and lag function are not getting the output I need. Please help. Thank you

I need to populate variable 'a' from previous value if missing

output needed;

a 1
a 2
a 3
d 4
d 5
g 6
;

data one;
input a $ b ;
datalines;
a 1 
b 2 
c 3
d 4
e 5
g 6 
;
data two;
set one;
if b in (2,3,5) then a='';
run;

data three;
set two;
retain c;
c=lag(a);
if a ='' then a=lag(c);
run;

[novinosrin]

data want;
set two;
retain _a;
if not missing(a) then _a=a;
else a=_a;
drop _a;
run;

[SuryaKiran]

Just assign C when not missing and retain those until the next non-missing.

data three;
set two;
retain c;
if not missing(a) then c=a;
run;