Date:         Sun, 22 Mar 2009 17:06:28 -0400
Reply-To:     Ian Whitlock <iw1sas@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Ian Whitlock <iw1sas@GMAIL.COM>
Subject:      Re: Do Loop: Insert Macro Value row by row
Comments: cc: OR Stats <stats112@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Summary: Efficiency issues
#iw-value=1

OR Stats,

You might shorten by combining steps 2 and 3.

   *append the results;
   data final;
          set final temp (in=temp) ;
          if temp then
          do ;
             m1=&macrovar1;
             m2=&macrovar2;
          end ;
   run;

If STUFF does not vary in the loop then it is hard to see how the
PROC SUMMARY produces different results.  If the summary step is not
adequately shown it may be possible to use a BY statement and
simplify the code and make it much more efficient.

You write, "Any comments on which types of steps run faster in SAS
would be good discussions too."

In general procedures will execute faster than corresponding well
constructed DATA steps.  A well constructed DATA step will execute
faster than a poorly constructed one.  In general the fewer steps
the better since it usually means fewer data passes.  If you want
more than perhaps it is best discussed in a particular context.

For example, if FINAL is big enough to be significant then

   *add in macro variables;
   data temp;
          set temp;
          m1=&macrovar1;
          m2=&macrovar2;
   run;


   *append the results;
   proc append base=final data=temp;
   run;

If FINAL is small enough then the first suggestion may be more
appropriate.

In general, writing for maintenance is more important than speed
unless the time is annoyingly large and done often enough.

In general, the design of data storage may be the greatest influence
on the amount of time spent writing and running programs.

Ian Whitlock
===============

Date:         Sun, 22 Mar 2009 07:26:50 -0500
From:         OR Stats <stats112@GMAIL.COM>
Subject:      Re: Do Loop: Insert Macro Value row by row
Comments: To: Andy Bowden <andybowden@gmail.com>

Thanks all for your reply.  I ended up using the following in case
it may be faster(?):


%do i = 1 to 10;


*create summary info;
proc summary data = stuff;
 output out=temp;
run;


*add in macro variables;
%let macrovar1=...;
%let macrovar2=...;


*Merge summary and macro info;
data temp;
       set temp;
       m1=&macrovar1;
       m2=&macrovar2;
run;


*append the results;
data final;
       set final temp;
run;


%end;


Any comments on which types of steps run faster in SAS would be good
discussions too.  Cheers

<snip>