SAS - Some Key References that Works on Rows of Variables List - Useful for Data Mining

SAS is famous for working column wise with efficient programming paradigm. However, often times, you want to work rows of variables as a way to analyze the ranking, importance, or values of variables list, per record.

The first important tool you need to consider rows of variables as data, which is not easy in the usual data structure implied in SAS.

The first one that aids in that direction is PROC SQL which creates rows of variables, not as a data set, but as a macro variables list. That is good, because you can call a macro to execute each of the variable name that is provided by the macro to work on specific columns of a sas data set.

A good reference here is http://support.sas.com/documentation/cdl/en/sqlproc/62086/HTML/default/viewer.htm#a001360983.htm

Suppose you want to work on collection of variables in a call, which may be dynamically changing then you need a tool to extract collection of variables. For example, you may extract all possible combinations of variables, each time as a subset, from a data set, to find out which is the best combination.

To do this you may use the following two macros depending upon whether you need combinations of variables or permutations of variables. 

All credit goes to SAS.  This is written, supplied, supported by SAS.  I just dumped here for my reference and usage.

"""""""
%macro permute(r) / parmbuff; /* the parmbuff option assigns */
%let i=2; /* the invocation parameter list to the */
%let things=; /* macro variable &syspbuff */
%do %while (%Qscan(&syspbuff,&i,%STR(,%))) ne ); /* scan the syspbuff */
%let p&i="%Qscan(&syspbuff,&i,%STR(,%)))"; /* to determine r */
%if &i=2 %then %let things=&&p&i; /* and count the number */
%else %let things=&things,&&p&i; /* of elements, n */
%let i=%eval(&i+1);
%end;
%let n=%eval(&i-2);
data permute;
drop i j copy;
array check (*) $ 10 r1-r&r; /* create a total of r */
%do m=1 %to &r; /* variables for looping */
do r&m = &things;
%end;
copy=0;
do i=2 to &r; /* look for duplicate items */
do j=1 to i-1; /* and keep the unique ones */
if check(j)=check(i) then copy+1;
end;
end;
if copy = 0 then output; /* writes to a SAS data set */
if copy = 0 then put r1-r&r; /* writes to the log */
%do m=1 %to &r;
end; /* end the r DO LOOPS */
%end;
run;
proc print uniform data=permute;
title "permutations of &n items taken &r at a time ";
run;
%mend permute;



%macro combo(r)/parmbuff;

%let i=2;
%let things=;
%do %while (%Qscan(&syspbuff,&i,%STR(,%))) ne );
%let p&i="%Qscan(&syspbuff,&i,%STR(,%)))";
%if &i=2 %then %let things=&&p&i;
%else %let things=&things,&&p&i;
%let i=%eval(&i+1);
%end;
%let n=%eval(&i-2);
data combo;
keep v1-v&r;
array word $8 w1-w&n (&things);
array rr (*) r1-r&r;
array v $8 v1-v&r;
%do i=1 %to &r; /* create the DO LOOPs */
%if &i=1 %then %do;
do r&i=1 to &n-(&r-&i);
%end;
%else %do;
do r&i=r%eval(&i-1)+1 to &n-(&r-&i);
%end;
%end;
do k=1 to &r; /* select subscripted items */
v(k)=word (rr(k)); /* for a SAS data set */
put v(k) ' ' @; /* for log */
end;
put; /* writes to log */
output; /* writes to a SAS data set */
%do i=1 %to &r;
end; /* create ENDs for the DO LOOPs */
%end;
put;
run;
proc print uniform data=combo;
title "combinations of &n items taken &r at a time ";
run;
%mend combo;

""""""""


Reference: http://support.sas.com/techsup/technote/ts498.html

So the idea here is create the combinations of variables using this macro and use the output as a dataset and read one row at a time and execute your macro.