SAS Notes

Compiled by : Wilson Suraweera @ CGHR

Contents: Random Numbers in SAS; Data Sub-setting; Selection of two Random Samples; Identification and Separation of duplicate records in SAS dataset; Reshape Long list variable dataset to Wide list dataset; Missing values replacement with Means of the respective Variables; Logistic Regression with SAS; SAS made easy using Proc SQL; SAS PROC SQL procedure to access external ODBC data sources; SAS String Data Handling; SAS Missing value arithmetic's
Update_a_Table_using_Another_Table_in_SAS: Text analysis - an Epidemiological Case Study by WS - SAS Institute HUG -01 April2011
External Resources: SAS Knowledge Base - Glossary of SAS Procedures from SAS.com; SAS resources from - UCLA; Logistic regression
Survival Analysis : Usage of Proc LifeTest and Proc PHREG: SAS Dinosaur - Old and New way of SAS programming; Paul Dicman's Web Page for SAS- This little old discusses SAS 8, but useful; Global Statements Dictionary - Alphabetical listing and Description of SAS Key words; SAS Study Blog; SAS Canada - User Groups

Missing value arithmetic



/*******************************************************************/
	/* Rule : Numeric missing value arithmetic **********
	
	let X Non-missing value
		Y Missing value
		
	Then 	 X+Y is a Missing value
		 X-Y is a Missing value
		 X*Y is a Missing value
		 X/Y or Y/X is a Missing value
**************************************************/
data test;
	x=2; 
	y=.; 
	z=.m; /* x: Numeric value, y: Missing value, z: Special missing value */
	
/* eg. Addition, subtraction, multiplication, division */

	add1=x+y; subs1= x-y; mult1= x*y; div1= x/y;
	add2=x+z; subs2= x-z; mult2= x*z; div2= x/z;
	add3=y+z; subs3= y-z; mult3= y*z; div3= y/z; 
	
/* Results of all add, subs, mult and div values are become missing*/
/* Exception */ 
	add4=sum(x,y);   /* Interesting ! add4=2 is a non missing */
run;

/* to see the result */

	proc print data=test;
	run;
	
/* Result 

Obs x y z add1 subs1 mult1 div1 add2 subs2 mult2 div2 add3 subs3 mult3 div3 add4 
1   2 . M .    .     .     .    .    .     .     .    .    .     .     .    2 
*/

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