Create V2 based on V1 and where V1 missing, assign the max value of V1 column

[Primohunter]

Hello everyone, i have a question regarding the creation of a column based on another, as you can read in the subject.
Example

HAVE DATASET:

V0    V1                 

1       23/11/22

2       24/11/22

3       .

4       21/11/22

WANT DATASET:

V0    V1                 V2  

1       23/11/22       23/11/22

2       24/11/22       24/11/22   

3       .                    24/11/22

4       21/11/22       21/11/22

Thank you all, in advance

[PeterClemmensen]

Try this

data have;
input V0 V1 :ddmmyy8.;
format V1 ddmmyy8.;
datalines;
1 23/11/22 
2 24/11/22 
3 .        
4 21/11/22 
;

data want;
   set have;
   if V1 then _iorc_ = V1;
   V2 = _iorc_;
   format V2 ddmmyy8.;
run;

Result:

V0  V1        V2
1   23/11/22  23/11/22
2   24/11/22  24/11/22
3   .         24/11/22
4   21/11/22  21/11/22

[PaigeMiller]

This doesn't seem to find the max value of V1 and use that in V2 when V1 is missing.

How about this:

proc summary data=have;
     var v1;
     output out=max max=v1_max;
run;
data want;
    if _n_=1 then set max;
    set have;
    v2=coalesce(v1,v1_max);
    drop _type_ _freq_ v1_max;
    format v2 ddmmyy8.;
run;