Count number of missing dates within group

[chinna0369]

Hi,

I have below data, how can I count number of missing dates within a group? Here I have provided only one id and one visit. I have large data. 

here number of missing dates by id and visit are 5 (20JUL2018, 21JUL2018, 22JUL2018, 24JUL2018, 25JUL2018).

data have;
input date $1-10 id $12-15 visit $17-25;
datalines;
19JUL2018  001  Baseline
23JUL2018  001  Baseline
26JUL2018  001  Baseline
27JUL2018  001  Baseline
28JUL2018  001  Baseline
;
run;

Thanks,

Chinna

[Ksharp · Accepted solution]

data have;
input date :date9. id $ visit $;
format date date9.;
datalines;
19JUL2018  001  Baseline
23JUL2018  001  Baseline
26JUL2018  001  Baseline
27JUL2018  001  Baseline
28JUL2018  001  Baseline
;
run;

proc sql;
create table want as
select id,visit,range(date)+1-count(distinct date) as n_miss_date 
 from have
  group by id,visit;
quit;