************************************************************
* Program:  C:\NHANES\CleanRecode_RecodeSkip               *
* Proposal: Code variable based on skip pattern            *
************************************************************;
libname NH "C:\your_dir";

/*change the name of the directory folder to the location that you saved your downloaded dataset
 from the sample code and dataset downloads module: for example "c:\nhanes\data"*/

/*Recode blood pressure variable based on skip pattern and
  create derived variable based on skip pattern*/

/*Recode option 1: Directly recode variable and check recoding*/
Data demo_BP2a;
	set NH.demo_BP1;
	If BPQ030=1 then BPQ030=1;
	Else if BPQ020 in (1,2) and BPQ030 <7 then BPQ030=2;
      Else BPQ030=.;

Proc freq data=demo_BP2a;
where ridstatr=2 and ridageyr>=20;
	table BPQ020*BPQ030/list missing;
	title 'Check recode BPQ030';
run;

/*Recode option 2: Create derived variable (diagHTN) 1-yes, 2-No*/
Data demo_BP2b;
	set NH.demo_BP1;
	If BPQ030=1 then diagHTN=1;
	Else if BPQ020 in (1,2) and BPQ030 <7 then diagHTN=2;

Proc freq data=demo_BP2b;
    where ridstatr=2 and ridageyr>=20;* interviewed and examined(ridstatr=2), adults age 20+;
    table diagHTN*BPQ020*BPQ030/list missing;
	title 'Check derived variable diagHTN';
run;