Non-Directional Concatenation

[saraturbow]

Hello! I am studying hospital admissions and readmissions and am trying to figure out how to concatenate two variables so that SAS creates the same value of the variable whether the patient was admitted first to hospital A then hospital B, or first to hospital B then A.

The best (clumsy) way I could come up with was to concatenate admission hospital-readmission hospital and then readmission hospital-admission hospital variables in different data sets, merge them, and then add their counts. The issue with this is that I am then double counting admissions. Thanks!

[PaigeMiller]

Can you show us a portion of the data you are using, and the desired output?

[saraturbow]

Yes--hope this snapshot helps. Each line of data is an admission-readmission dyad and I am trying to determine the number of admissions to each pair of hospitals. When I concatenate the admissionhospid and readmissionhospid and count their frequencies, 'AB' and 'BA' are counted separately, but I would like them to be counted together.

admissionhospid  readmissionhospid

A                           B

B                           A

A                           C

B                           C

[Reeza]

Updated my answer, to use your sample data.

[Reeza · Accepted solution]

Sort them alphabetically first, assuming that names will be identical. Using that rule the two same hospitals should always appear in the same order. I also upcased them, and you may need compress/trim if the names are not 100% identical each time.

HospitalStart = upcase(Hospital1);
HospitalEnd = upcase(Hospital2);
call sortc(HospitalStart, HospitalEnd);
want = catx("-", HospitalStart, HospitalEnd);

You could probably nest those in some fashion but I spelled it out so it's clear how it works.

data have;
input admissionhospid $ readmissionhospid $ ;
cards;
A                           B
B                           A
A                           C
B                           C
;;;;
run;

data want;
set have;

HospitalStart = upcase(admissionhospid);
HospitalEnd = upcase(readmissionhospid);
call sortc(HospitalStart, HospitalEnd);
option1 = catx("-", HospitalStart, HospitalEnd);

if admissionhospid < readmissionhospid then option2 = catx("-", admissionhospid, readmissionhospid );
else option2 = catx("-", readmissionhospid, admissionhospid );


run;

Results:

Obs	admissionhospid	readmissionhospid	HospitalStart	HospitalEnd	option1	option2
1	A	B	A	B	A-B	A-B
2	B	A	A	B	A-B	A-B
3	A	C	A	C	A-C	A-C
4	B	C	B	C	B-C	B-C

[saraturbow]

Thank you! Will try this!

[ballardw]

Readmission frequently happens more than once and admission may as well over time.

So you need to provide some pretty clear rules about which are initial admissions and which re-admissions might be associate with a specific admission.

I suspect that date information may be helpful but examples are needed to provide good workable approaches.