Logical variables in SAS
Logical variables:
We are working based on 2 variables
- First.Variable
- Last.variable
- If First. variable is 1, then we will get first occurrence.
- If First. variable is 0, then we will get remaining occurrence except first occurrence.
- If Last. variable is 1, then we will get last occurrence.
- If last. variable is 0, then we will get except last occurrence include first occurrence.
/* To report first occurrence information */
Ex:
Data medi;
Input Gid $drug$ sdate edate ;
Informat sdate edate date9.
Format sdate edate date 9;
Cards;
G100 col5mg 12jan2006 16jan2006
G101 col5mg 13jan2006 17jan2006
G102 col5mg 13jan2006 17jan2006
G101 col10mg 21jan2006 25jan2006
G102 col5mg 23jan2006 27jan2006
G100 col10mg 23jan2006 29jan2006
G100 col15mg 01feb2006 05feb2006
G101 col10mg 03feb2006 07feb2006
G102 col15mg 03feb2006 06feb2006
G103 col10mg 03feb2006 04feb2006
;
Proc sort data = medi;
By Gid;
Run;
Proc print data =medi;
Run;
Data first;
Set medi;
By Gid;
If first .gid =1;
Run;
Proc print data =first;
Run;
/* To report remaining occurrence except first to report each and every patient except first visit information*/
Ex;
Data remain1;
Set medi;
By gid;
If first.gid=0;
Run;
Proc print data=remain1;
Run;
/* To report last occurrence –subject of each patients last visiting information*/
Ex:
Data last;
Set medi;
By gid;
If last.gid=1;
Run;
Proc print data=last;
Run;
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/* To report each and every patients visiting information except last visit information*/
Ex;
Data remain2;
Set medi;
By gid;
If last.gid=0;
Run;
Proc print data=remain2;
Run;
/* To report first and last occurrence information*/
Ex;
Data firstlast
Set medi;
By gid;
If first.gid=1 or last.gid =1;
Run;
Proc print data=firstlast;
Run;
/* To report which group visited only once*/
Ex;
Data flast;
Set medi;
By gid;
If first.gid=1 and last.gid=1;
Run;
Proc print data=flast;
Run;
/* To report remaining occurrence except first and last*/
Ex;
Data remain3;
Set medi;
By gid;
If first.gid=0 and last.gid=0;
Run;
Proc print data=remain3;
Run;
Retain statement:
It can be used to calculate running total or cumulative tools.
- Using retain statement, we can reassign required variables current data value.
- If we omit 0, it default stores dot(.).
Ex:
Data market;
Input month $sale;
Cards;
Jan 200
Feb 300
Mar .
Apr 400
May 500
June 200
;
Data market 1;
Set market;
Retain total 0;
Total = sum (total, sale);
Run;
Proc print data = market1;
Run;
To generate the output window with out using any procedure application(use with data set block)
Ex;
Data _null_;
Set market;
File print;
Put month sale;
Run;
Null data set creation:
(with variable and with out observations) using with data set block
/* To delete required observations from existed data set*/
Ex:
Data market ;
Set market;
If sale < 400 then delete;
Run;
- If we run delete statement without any condition it delete overall data from existing data set.
Ex:
Data market1 ;
Set market;
delete;
Run;
Ex:
Data market1 ;
Set market;
If sale >=400 ;
Run;
/* null data set creation */
Ex:
Data demo;
Length pid 4 age 3
Race $ 6;
delete;
Run;
- -Null-, without data set creation.
- Null data set, with variables and with out observations.
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