Even you can Use HASH and DOUBLE DASH: It’s that Simple……

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

1 1 2 3 4 5

DOUBLE DASH OUTPUT:

Obs var1 var2 var3 COL var4 var5
1 1 2 3 1 4 5

Renaming All Variables in a SAS Data Set Using the SASHELP VIEWS

*Create a temporary dataset... DSN;
data dsn;
a=1;
b=2;
c=3;
d=4;
e=5;
f=6;
run;


%macro test(lib,dsn);

*/1)*/ data _null_;
set sashelp.vtable(where=(libname="&LIB" and memname="&DSN"));
call symput('nvars',nvar);
run;

*/2)*/ data dsn;
set sashelp.vcolumn(where=(libname="&LIB" and memname="&DSN"));
call symput(cats("var",_n_),name);
run;

*/3)*/ proc datasets library=&LIB;
modify &DSN;
rename
%do i = 1 %to &nvars;
&&var&i=Rename_&&var&i.
%end;
;
quit;
run;
%mend;

%test(WORK,DSN);

After submitting the above program... the output looks like this....

Output:
Rename_a Rename_b Rename_c Rename_d Rename_e Rename_f
1 2 3 4 5 6

Here is a way I know of.. to rename all the variables in the dataset;

It can be done using the SASHELP views as follows:

1) The 1st step of the program determines the total number of variables inside the dataset with the help of SASHELP.Vtable, Data _null_ step used to do the same …. A macro variable NVAR (Number of Variables) will be created after this step which can be accessed in the following steps.

2) What the 2nd step does is….assigns a unique IDNUM to all the variables of the dataset with the help of SASHELP.Vcolumn.

3) What the 3rd step does is … it uses Proc Datasets with the MODIFY statement to rename all the variables in the dataset. The DO LOOP is been used to resolve the 6 macro variables in a macro of a temporary dataset.