Date:         Thu, 23 Feb 2006 12:47:59 -0800
Reply-To:     "Terjeson, Mark (IM&R)" <Mterjeson@RUSSELL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Terjeson, Mark (IM&R)" <Mterjeson@RUSSELL.COM>
Subject:      Re: Help on macro
Content-Type: text/plain; charset="us-ascii"

To our original poster,

Re: Keeping the learning and using of macros straightforward at first.

Many, many good thoughts, comments, and book references have
been posted.  I very much second David's thoughts to get
familiar with datastep and procs first.  We've all seen when
the few venturesome folks dive into macros while still in the
early learning stages of SAS, get into overly confusing design
attempts (as David puts, miserable messes).  Just as David
eludes to, it's best to only start wanting to employ SAS macros
when situations of repetition arise (with consolidating the
repetition aspects the emphasis) or when needing "dynamic"
parameter feeding.  People familiar with other programming
language or application background where macro coding is
available, where "macros" in those environments really do
general processing, often have a tough time getting a hold
of the misconception (or perception) that SAS macros actually
do general processing in the same sense.  SAS Institute's macro
facility may be quite different conceptually but is actually quite
simple in concept and many times allows for even more complex
dynamic solutions.  Folks in our neck of the woods find the idea
of "text-substitution" is a quick way to wean themselves from the
misperceptions and grasp the power and flexibility in SAS macros.

A very elementary LayPerson's Macro-101 can be found at:
http://listserv.uga.edu/cgi-bin/wa?A2=ind0512B&L=sas-l&P=R29031

Even as folks become intermediate and advanced users of SAS,
I ditto David's recomendation "Try not to fall into that trap",
of using SAS macros too often or too early, until you gain an
understanding of where they are best applied.

Lots of times nowadays, good, normalized data and 4GL joins can
actually replace the interaction of 3GL parameters and processing.


Hope this is helpful.


Mark Terjeson
Senior Programmer Analyst, IM&R
Russell Investment Group


Russell
Global Leaders in Multi-Manager Investing








-----Original Message-----
From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of
David L Cassell
Sent: Thursday, February 23, 2006 11:39 AM
To: SAS-L@LISTSERV.UGA.EDU
Subject: Re: Help on macro


kog@SSB.NO replied:
>Hi, you are indeed asking a lot here.. The subject line could well
>read: "Please teach me a lot about this macro facility". You can't
>expect that to happen. You'll need to study yourself, by practising and

>reading. Besides the SAS documentation a really good book is
>Carpenter's:
>http://www.sas.com/apps/pubscat/bookdetails.jsp?catid=1&pc=59224

> >I am new to SAS as well new to SAS Macro.
>
>A good advice, if you are new to SAS/Base in general: *wait* with macro

>coding. Many questions on macro here indicate that quite a few should
>focus more on the Base language (i.e. open code) before jumping on to
>macros. It's up to you though..
>
> >It would great help if you
> >could help me.
> >The below are few questions which i would like to  know
> >
> >1)why macros are used and when should we think of writing macros(on
> >what basis),what are things we should look before writing macros.
>
>Macros generate code, so it is often used when there are patterns in
>the code. Conditionally generating code is another imp. aspect, for
>example based on parameters you supply.
>
>
> >2)Can we use SAS variable inside the macro,if not why?
>
>The macro part is compiled and executed prior to the datasteps and
>procs, so the answer is kind of "no".
>
> >3)when to use &,&&,and &&&,how do we distinguish.
>
>Read all about it in the docs or Carpenter's book.
>
> >4)what is the diff between Single dot and double dot(eg. &chech. and
> >&check..)
> >
>
>See [long URL]
>
>http://support.sas.com/documentation/onlinedoc/91pdf/sasdoc_91/
>base_macro_6997.pdf
>
>page 28.

Okay, first I wanted to say that this was a great response.

Then I wanted to babble a bit to our original poster.

People have a tendency to leap into SAS macros too early, in my opinion.
SAS macros are a *huge* and invaluable tool.  But if you only know
macro, then everything looks like a macro problem.  So take everyone's
advice and focus on SAS data steps and procs first.  Learn what you can
do without macro, so you will better understand when you do want to use
the tools.

As Arild and others have said, SAS macro gives you the ability to
generate text.  (Essentially) once that text has been written out, then
the SAS code gets run.  So trying to mix SAS code and macro code gets
most beginners into miserable messes.

SAS macro code can help a lot if you have a problem like:

[1] You have to do one process if the data set has less than 1000
records, and a different process if the data set has at least 1000
records.

[2] You have a pile of maybe a hundred repetitive IF-THEN-ELSE
statements that could all be generated automatically if only you had a
text generator.


The problem is that people learn some macro basics, and then they start
using SAS macro to do stuff for which SAS has better tools.  Tools they
don't use yet, because they learned about macros instead of learning
more about data steps and procs first.  Try not to fall into that trap.

HTH,
David
--
David L. Cassell
mathematical statistician
Design Pathways
3115 NW Norwood Pl.
Corvallis OR 97330

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