Imput missing data with avaiable values

[mkt_apprentice]

Hello SAS members,

I merged some data sets and got some missing values in my new merged data set. Currently it looks like this:

ID     Date          Age        Group             Workout_mins

1       1                 35           35                   60

1       2                   .             .                     45

1       3                   .             .                      0 

 ...

So basically age and group stay the same, how can I imput the values based on existing values to the . in the data set (i.e. "." => 35, etc.)

Thanks!

[novinosrin]

Not clear with this  "." => 35, 

do you want missings to be imputed with previous non missing value?

if yes

data have;
input ID     Date          Age        Group             Workout_mins ;
cards;
1       1                 35           35                   60
1       2                   .             .                     45
1       3                   .             .                      0 
;

data want;
update have(obs=0) have;
by id;
output;
run;

[mkt_apprentice]

Yes, since the person with ID 1 is 35 years old as seen in the row above, the . in the below row should be the same value (35). Could you explain what is 

have(obs=0) have

in your codes? 

[novinosrin]

@mkt_apprentice  some reading about update statement here http://support.sas.com/documentation/cdl/en/basess/58133/HTML/default/viewer.htm#a001329151.htm

will help you

[mkt_apprentice]

Thank you for the reference reading!
I got that "want" is the newly modified data set by revising master data set "have(obs=0)" by the information in the data set "have". Could you help explain what does "have (obs=0)" refer to? Obs is not a variable right, so what does obs=0 refer to?

[VDD]

data have;
input ID     Date          Age        Group             Workout_mins ;
cards;
1       1                 35           35                   60
1       2                   .             .                     45
1       3                   .             .                      0 
;

data want;
retain h_age 0;
set have;
if first.id then h_age = age;
if age <= h_age then age = h_age;
by id;
drop h_age;
run;

[mkt_apprentice]

Hi VDD, what does 0 in the second coding line indicate (retain h_age 0)?