Conditional Merging in SAS - sas

Question

Hi all i have the below two datasets in which i need to map Date1 with Date2 in a range of (+/- 7)days within an ID.
Data set1;
input ID Date1 ddmmyy8.;
Format Date1 Date11.;
Datalines;
001 02-08-15
001 04-08-15
001 06-08-15
002 11-09-15
002 14-09-15
002 17-09-15
;
run;
Data set2;
input ID TYPE $ Date2 ddmmyy8.;
Format Date2 Date11.;
Datalines;
001 TYPE1 02-08-15
001 TYPE2 11-08-15
001 TYPE3 06-08-15
002 TYPE1 07-09-15
002 TYPE2 04-09-15
002 TYPE3 09-08-15
;
run;
Proc sql;
create table out as select a.ID, a.Date1, b.Date2,
intck('days', Date1, Date2) as Diff
from set1 as a full join set2 as b
on a.ID = b.ID and (Date1 + 7 >= Date2 >= Date1 - 7)
group by a.ID, Date1 having diff = min(diff);
quit;
I get the below output
i need output
Expected Output
***The output i get is highlighted in yellow when i map using min of Diff.
but the output i need is highlighted in green it is because i have to maintain the values in Date2 as distinct and does not repeat.
(i.e) Because 02-Aug-2015 is already mapped with 02-Aug-2015 as well as 09-Aug-2015 mapped with 09-Aug-2015 of Date1 i need the 04-Aug-2015 of Date1 to be mapped with the remaining 11-Aug-2015***

Answer 1

So judging on the comments above the rules are quite complex:
* join based on ID
* Absolute difference between date 1 and date 2 should be less then 7
* Preference for matching dates should be given to dates that are equal
* In case dates aren't equal, the solution should be so that as much as combinations are
returned as possible
* Date1 & Date2 need to be unique
I'm not sure whether the solution can be done in one proc sql step.
You can't just work with a simple rule as it is not always the result with the lowest difference between dates that needs to be returned. Next to that, you need to sort of 'remember' which dates per ID you have selected for an output since you can't select them anymore further on.
First I made an inner join on ID where the difference in dates was <= 7. This gives all possible valid combinations. Then I've put all the dates where the difference in dates was 0 in a macro variable so I can make a table of all possible combinations except dates being in the macro variable. In the last step then you want to have the solution returning the most possible combinations of date1 - date2 where both are distinct.
Data set1;
input ID Date1 ddmmyy8.;
Format Date1 Date11.;
Datalines;
001 02-08-15
001 04-08-15
001 06-08-15
002 11-09-15
002 14-09-15
002 17-09-15
;
run;
Data set2;
input ID TYPE $ Date2 ddmmyy8.;
Format Date2 Date11.;
Datalines;
001 TYPE1 02-08-15
001 TYPE2 11-08-15
001 TYPE3 06-08-15
002 TYPE1 07-09-15
002 TYPE2 04-09-15
002 TYPE3 09-08-15
;
run;
Proc sql noprint;
/*Create a macro variable with all the dates for which the difference between date1
and date2 = 0 */
select distinct put(Date1,yymmddn8.) into: dates seperated by ','
from set1 as a inner join set2 as b
on a.ID = b.ID and abs(intck('days', Date1, Date2)) = 0;
/*Create table with all lines where difference <= 7 but date is not in the ones with
difference = 0 */
create table out as select a.ID, a.Date1, b.Date2,
intck('days', Date1, Date2) as Diff
from set1 as a inner join set2 as b
on a.ID = b.ID where abs(intck('days', Date1, Date2)) <= 7 and
find("&dates.",put(Date1,yymmddn8.)) = 0 and find("&dates.",put(Date2,yymmddn8.)) = 0;
/* Check the number of possible combinations */
create table out as
select a.*,
b.cnt1 + c.cnt2 as combos
from out a left join (select distinct id,
date1,
count(*) as cnt1
from out
group by id, date1) b on a.date1 = b.date1 and a.id = b.id
left join (select distinct id,
date2,
count(*) as cnt2
from out
group by id, date2) c on a.date2 = c.date2 and a.id = c.id
order by id, combos;
quit;
/* Select unique dates per date1, date2 */
data out(keep = id date1 date2);
retain mem1 mem2;
length mem1 mem2 $100.;
set out;
by id combos;
if first.id then do;
mem1 = "0";
mem2 = "0";
end;
date10 = put(date1,yymmddn8.);
date20 = put(date2,yymmddn8.);
if find(mem1,date10) = 0 and find(mem2,date20) = 0 then do;
mem1 = catx(',',mem1,date10);
mem2 = catx(',',mem2,date20);
output;
end;
run;
/* Create a union between lines with no difference in date and lines with difference
in date*/
proc sql;
create table final as
select * from out
union
select a.ID, a.Date1, b.Date2
from set1 as a inner join set2 as b
on a.ID = b.ID and abs(intck('days', Date1, Date2)) = 0;
quit;
So this gives a table like:
Final Table