Tracking variables creations and temporary variable creation in SAS

Tracking variables creations and temporary variable creations:

Using this concept, we can report matching observation or non matching observation from required data set. Tracking variable can be created by in option. If tracking variable value is 1 we get matching variable, if tracking variable value is 0 we get non matching variable. /* To report each and every patient SBP information with drug information after taken the treatment*/               Data trt; Infile ‘d:\trt.txt’; Input pid drug $sbp; Cards; Data suc; Infile ‘d:\sucess.txt’; Input pid sbp; Cards; Data fail; Infile ‘d:\fail.txt’; Input pid sbp; Cards; Proc sort data =txt; By eid; Run; Proc sort data =suc; By eid; Run; Proc sort data =fail; By eid; Run; To import the data are txt, suc, fail. Sorting the 3 data sets based on matching variables. /* To update txt with suc*/ Data txt; Update txt suc (in = var); By pid; If var =1 then statue =’sucess’; Run; /* To update txt with fail*/ Data txt; Update txt fail(in = var); By pid; If var =1 then statue =’failure’; If status = ‘ ‘ then Status = ‘change’; Proc print data =txt; Run;

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Modify statement:

It can be used to replace the data values (from update the data values) manipulating data, delete observations, modifications.

• Modification can be done by using set statement or modify statement
• Using set statement we can do modifications in existed data set using expressions.
• Using modify statement we can do modification in existed data set using expressions and another data set values.

Ex: Data emp; Input eid salary ; Cards; 100  4000 101  8000 ; /* use with set */ Data emp; Set emp; Salary =salary +1000; Run; /* use with modify*/ Data emp;   Set emp; Run; Proc print data =emp; Run; Note: Using set statement we can do modifications and these modifications can be stored in new variable and new data set or existed variable and existed data set. Using modify statement we can do modifications and these modifications can be stored in existed data set or existed variable. /*To do modification in one data set to another data set */ Syntax: Modify <master file> <transition file>; By <matching variable>; Ex: Data emp; Input eid salary  ; Cards; 100  3000 101  2000 102  4000 ; Data emp1; Input eid   bonus; Cards; 100  500 102  1000 101  200; Proc sort data = emp1; By eid; Run; Data emmp; Modify emp emp1; By eid; Salary =salary +bonus; Run; Proc print data =emp; Run;

/* To reporting patient SBP after taken the treatment drug information */

Ex: Data medi; Input stno drug$ sbp; Cards; 100 col5mg 156 101 col5mg 159 102 col10mg156 103 col10mg145 104 col15mg167 ; Data success; Input stno srate :percent3; Cards; 100  50% 102  40% 100  30% ; Data fail Input stno frate : percent 3.; Cards; 101  20% 104  10% ; Proc sort data =medi; By stno; Run; Proc sort data =success; By stno; Run; Proc sort data =fail; By stno; Run;

/* To modify medi use with success*/

Ex: data medi; Modify medi success; By stno; Sbp= sbp * srate; Run; /* To modify medi use with fail*/ Ex: data medi; Modify medi fail; By stno; Sbp= sbp+(sbp *frate); Run; Proc print data =medi; Run;  

/* To replace the master data set values with transition file using modify statement*/

Ex: Data emp; Input eid salary  ; Cards; 100  5000 101  4000 ; Data emp1; Input eid   nsal; Cards; 101  7000 100  6000 ; Proc sort data = emp; By eid; Proc sort data = emp1; By eid; Run; Data emp; Modify emp emp1; By eid; Salary =n sal; Run; Proc print data =emp; Run; Case 1:       Non matching observation (non obs) occurred in master file we can run the modify statement. Case 2:       Non matching observation (non obs) occurred in transition we can’t run the modify statement(modify statement does not have appending capability). Case 3:       Non matching variable occurred in master file, we can run the modify statement. Case 4: Non matching variable occurred in transition file, we can’t run the modify statement.

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