In order to understand HASH and DOUBLE HASH concept in SAS you need to know about two different ranges of variables:
1) Numbered list:
When a set of variables have the same prefix, and the rest of the name is a consecutive set of numbers, we can use a single dash (-) to refer to an entire range. Some exs.. are….
VAR1 VAR2 VAR3 VAR4 VAR5
Shortcut list you can use to access all 5 variables is VAR1-VAR5
COL1 COL2 COL3 COL4 COL5 COL6 COL7
Shortcut list you can use to access all 7 variables is COL1-COL7
2) Name range list:
When you refer to a list of variables in the order in which they were defined in the SAS dataset, you can use a double dash (--) to refer to the entire range of variables in between them.
Ex: VAR1 VAR2 VAR3 COUNT VAR4 COL1 VAR5
Shortcut list you can use to access all 7 variables (including COL1, which has different prefix name than others) is VAR1- -VAR5
The general rule you should always remember for dash and double dash is:
Single dash is useful to access the consequently numbered variables.
Double dash is useful to access variables based on their order/position regardless of variable name.
Execute following program in SAS to understand the concept better.
data test;
var1=1;
var2=2;
var3=3;
COL=1;
var4=4;
var5=5;
run;
ods listing close;
ods rtf file="Single DASH output.rtf" style=rtfout;
title1 'Using Single DASH';
proc print data=test;
var var1-var5;
run;
ods rtf close;
ods trace off;
ods listing;
ods listing close;
ods rtf file="Double DASH output.rtf" style=rtfout;
title1 'Using DOUBLE DASH';
proc print data=test;
var var1--var5;
run;
ods rtf close;
ods trace off;
ods listing;
SINGLE DASH OUTPUT:
Obs var1 var2 var3 var4 var5
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