How to export case ID numbers that the 2 controls matched with in the matching step?

Denali — Fri, 22 Oct 2021 15:14:18 GMT

Hi,

I used the SAS code from this article (https://www.frontiersin.org/articles/10.3389/fdata.2019.00004/full) to do 1:2 matching for 1 case with 2 controls.

Does anyone know how to generate a column with case ID numbers that the 2 controls matched with in the "matches" file step?

/*Example Code*/

DATA population; /*Example of population dataset*/

input uniqueid gender $ age ethnic $ casecontrol; /*gender and ethnic are defined as categorical variables by the following $*/

cards;

1 f 26 1 1

2 m 27 1 1

3 m 30 2 0

4 f 25 2 0

5 m 29 1 0

6 f 26 1 1

7 f 28 2 0

8 f 28 1 0

9 m 25 1 1

10 m 26 2 0

11 f 30 3 0

12 m 29 2 0

13 f 27 1 0

14 m 27 3 0

15 f 26 1 1

16 f 25 2 0

17 f 29 1 0

18 f 30 3 0

19 m 26 1 0

20 m 26 2 1

21 f 30 2 0

22 m 25 3 0

23 m 27 1 0

24 m 28 1 1

;

run;

%LET agerange = 5; /*For this example, we have chosen the age range to be 5. Controls can therefore be up to 5 years younger or older than the case*/

%LET ratio = 3; /*We have chosen to match 3 controls for each case*/

DATA cases controls;

SET population;

IF casecontrol = 1 THEN OUTPUT cases;

ELSE OUTPUT controls;

RUN;

PROC FREQ NOPRINT DATA=cases;

TABLES age*gender*ethnic/OUT=caseout; /*Since we want ‘ethnic’ to be a matching variable, we need to add it here*/

RUN;

%MACRO sample(v_age, v_gender, v_count,v_ethnic); /*Here, ethnic is also added*/

DATA qualify1;

SET controls;

WHERE (&v_age-&agerange <= age <= &v_age+&agerange)

AND

(gender = "&v_gender")

AND

(ethnic = "&v_ethnic"); /*You will also need to add your extra variable to this step.*/

case_age = &v_age;

case_gender = "&v_gender";

case_ethnic = "&v_ethnic"; /* You will also need to add your extra variable to this step.*/

SEED = RANUNI(0);

PROC SORT;

BY SEED;

DATA qualify2;

SET qualify1 NOBS=totobs;

IF _N_ <= &v_count*&ratio;

IF &v_count*&ratio <= totobs THEN tag = 'yes';

ELSE tag = 'no';

PROC APPEND BASE=matches DATA=qualify2 force; /*new data set matches will contain the matched controls*/

PROC SORT DATA=qualify2 OUT=temp1 (KEEP=uniqueid);

BY uniqueid;

PROC SORT DATA=controls OUT=temp2;

BY uniqueid;

DATA controls; /*the dataset controls is updated so that the controls already matched are removed and can not be matched again*/

MERGE temp1(IN=in1) temp2(IN=in2);

BY uniqueid;

IF in2 AND NOT in1;

%MEND sample;

DATA _NULL_;

SET caseout;

CALL EXECUTE ('%sample('||age||','||gender||','||count||','||ethnic||')'); /* You will also need to add your extra variable to this step.*/

RUN;

/*The next part is for testing if any of the cases have not received the wanted amount of controls*/

PROC FREQ NOPRINT DATA=matches;

TABLES case_age*case_gender*case_ethnic/OUT=con_out; /* You will also need to add your extra variable to this step.*/

PROC SORT DATA = caseout(RENAME=

(age=case_age gender=case_gender count=case_cnt ethnic=case_ethnic)); /* You will also need to add your extra variable to this step.*/

BY case_age case_gender case_ethnic; /* You will also need to add your extra variable to this step.*/

PROC SORT DATA = con_out (RENAME= (count=con_cnt));

BY case_age case_gender case_ethnic; /* You will also need to add your extra variable to this step.*/

DATA final (DROP=percent);

MERGE caseout con_out;

BY case_age case_gender case_ethnic; /* You will also need to add your extra variable to this step.*/

con_need = case_cnt*&ratio;

IF con_cnt = . THEN con_cnt = 0;

diff = con_cnt-con_need;

PROC PRINT DATA = final; /*creates a table showing what characterizes the cases who have not received enough matches and how many matches they are missing*/

WHERE diff < 0;

TITLE 'Insufficient Matches';

RUN;

Thank you all in advance.

Re: How to export case ID numbers that the 2 controls matched with in the matching step?

PeterClemmensen — Fri, 22 Oct 2021 18:14:50 GMT

I can't figure out what you want to do here.

Please specify your desired result given the test data set.

topic How to export case ID numbers that the 2 controls matched with in the matching step? in SAS Programming

How to export case ID numbers that the 2 controls matched with in the matching step?

Re: How to export case ID numbers that the 2 controls matched with in the matching step?