Help with data manipulation in data step

[LucyLou]

Hi All,

I am trying to link records in my data by whether a few conditions apply. I want to create a new variable to determine contact with an infected classmate. I have my data so that for every day a student is in a particular school there is a separate record. I want to create a new variable "contact" that indicates whether a student was at the same school on the same day as any of the infected students (does not matter if it was one infected student or 10). I also need a way to prevent it saying it was in contact with an infected student if the infected student was himself (I hope that makes sense).

Please help!

Thank you in advance.

[lloydc]

I may be mis-reading your question and if so, I apologize. But it sounds like you can have a dataset (healthy) with variables     (school, student, date-attended) and another dataset (infected) with variables (school,infected-student,date-attended) then do a merge:

proc sort data=healthy; by school date-attended;

proc sort data=infected; by school date-attended;

data mergem;

set healthy; by school date-attended;

set infected; by school date-attended;

merge healthy (in=inh) infected (in=inf);

if inh and inf then output;

proc sort data=mergem; by student infected-student;

proc freq data=mergem; tables student*infected-student;

I think that would give you a table by healthy-student and each infected-student with the # of potential interactions for each combination.

Hope this helps.

[PGStats]

I will make a slightly different guess about your data structure and assume you have a single dataset with variables School, Student, Date, and Contagious. The following query would give you useful information (untested) :

proc sql;

create table contact as

select

     A.school,

     A.student,

     coalesce(count(distinct B.student), 0) as nbStudents,

     min(B.date) as firstContact format=date9.,

     max(B.date) as lastContact format=date9.

from

     (select * from attendance where not contagious) as A left join

     (select * from attendance where contagious) as B

          on A.school=B.school and A.date=B.date and A.student ne B.student

group by A.school, A.student;

quit;

PG

[LucyLou]

I think this worked! Thank you so much.