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Wednesday, March 28, 2007

SAS Programming Google Search

I have added a custom SAS programming search button to the top of this blog. It is done through Google Co-op and should offer better SAS programming search results than just searching the web.

You can use it directly from this blog, or you can add it to your Google homepage. To add it to your Google homepage click on the button "Add To Google".

I have not added/filtered many sites in it yet, but already I can see the results are more specific for SAS programming than just searching the web.

If you see sites that don't belong in the search result or if you know of a site that should have appeared in a search result but for some reason didn't, please comment here. The more I am able to refine the results, the better the SAS programming search will be. Soon, I would also like to start taging the sites in the search results. If you have suggestions for tags, that would be useful too.
Happy Searching!

Thursday, March 22, 2007

Not Equal

A long long time ago (or what seems like a long time ago!), before I could could call myself a professional SAS programmer I made lots of little mistakes in my programs. Now that I have been programming for a long time and have lots of good habits, I generally tend to avoid the little mistakes. Now when I make a mistake it is generally one of the bigger varieties. :)

One of the little mistakes I remember making was using the wrong "not equal" operator. It was terribly embarrassing for me at the time, and for some reason it stuck in my memory more than the other myriad mistakes I made.

When I first got hired as a SAS programmer, I did not have a whole lot of SAS experience. I had coded quite a bit growing up, but had only used SAS in a limited function at Texas A&M Univ on Windows. In my interview I explained my SAS skills honestly, and lo-and-behold they hired me! I was hired as an "intern" and had a few months to prove myself. I was told they needed people with PC experience because most of the programmers came from a mainframe MVS TSO background (which meant nothing to me at the time) and there were going to be more PC SAS contracts coming. Well, the PC SAS contracts never appeared and I suddenly found myself knee-deep in MVS TSO and mainframe SAS. JCL, ISPF, pf8 forward, pf7 back, pf3 end-- all new to me. It was all terribly daunting and every day I came to work, I thought someone was going to ask me to leave. So I did my best to keep my head above water and learn everything as quickly as I could. I thought I was doing a pretty good job masquerading as a true-blue mainframe developer until I wrote one of my first full programs and had another programmer look at it (the first week or two was spent making small changes to other people's programs and going through logs, etc). The reviewer wanted to know what this line meant:

if x <> y then delete;

I answered "if x not equal y then delete the row." The mainframer shrugged and gave me the benefit of the doubt that I knew what I was talking about. That was until someone else (one of the programmers employed by our client-- GULP!) looked at it and pointed out in a friendly email to everyone that <> is "not equal" in BASIC, but means something entirely different in SAS. I could feel everyone looking at me differently and hear their whispers.

"Basic? Basic? Is this kid a joke?" I had been exposed as a commodore 64 hack!

Well, luckily I wasn't fired and ended up learning a tremendous amount from those mainframe SAS programmers at my first real consulting job. I truly owe them my career.

So, what does <> mean in SAS? It is the MAX operator and returns the maximum of the two values on either side of it. Conversely >< is the MIN operator and returns the smaller of the two values.

Oh wait! We're talking about SAS here, right? Then I should say <> is _usually_ the max operator, but in one situation, it can stand in as the "not equals" operator I was intending it to be.

Proc SQL of course!

Friday, March 09, 2007

The =: Operator

Most people who are familiar with programming SAS are familiar with the equal colon operator ( =: ). There are a couple different colon operators in SAS, but in this post I am only talking about the comparison operator. The equal colon operator works much like the substr() function. It is used to compare substrings for equality.

Here is a quick little example:

data _null_;
x = 'abcdefg';
if x =: 'abc'
then put 'The substrings match.';

As you can see if you run the little data step above the substring 'abc' matches in 'abcdefg'. A better way to think of it is that it "starts with" the substring. The same could also be accomplished by this statement:

if substr(x,1,3) = 'abc'
then put 'The substrings match.';

There is one big difference between the =: operator and using substr(). With the substr() function you tell it exactly how many characters to look for the substring. In the example above it was three. For the =: operator it has to figure out how many characters to search. It does this by (somewhat counter-intuitively) looking at _both_ sides of the operator to find the shortest length. Here is an example:

data _null_;
x = 'abcdefg';
if x =: 'abc'
then put 'The substrings match.';

If you run the above data step you will see that they match. It looks a little funny because most of us assume that SAS is looking for 'abcdefg' within 'abc', but that's not really what's happening. SAS uses the shortest string to decide what to look for, no matter which side of the equals sign it is on.

Oh yeah, the =: operator also works in list context such as:

if x in: ('abc', 'xyz', 'def');

That's it for today's post. Happy coding!