The Sum Function

Today's function is very straightforward. It adds numbers.

num = sum( argument, argument, ... );

So straightforward in fact, that some of you new to SAS may be wondering why you might even need such a simple function? There's certainly nothing wrong with the old "+ sign" right? Well, the sum() function can do something that the plus sign cannot do. And that is treat missing values as if they are 0. That can be a very important distinction if there is the possibility of adding variables that may contain missing values.

Consider the following data step:

data _null_;
  a = 1;
  b = 2;
  c = .; * our missing value;

  r1 = a + b + c;
  r2 = sum( a, b, c );
  put r1=;
  put r2=;
run;

The value of r1 will be missing since the plus operator returns missing if one of it's arguments is missing. The value for r2 will be 3 since it treats the missing value as if it were a 0

Another SAS Function Friday

Friday again already?! Doesn't it seem like time speeds up around Autumn? Something about the shortening days, the changing weather, the new TV line-up, the expectation of the holiday season soon approaching... I dunno, maybe it's just me?

For some crazy reason all this ruminating on days shortening kinda reminds me of one of my favorite SAS functions: intnx(). How's that for a weak tie-in? :)

Intnx() is used to increment a SAS date/time/datetime value by a given interval and returns a SAS date/time/datetime value. The following syntax should be enough to get you started, refer to SAS documentation for more details:

dt = intnx( 'INTERVAL', dateTime, increment <,alignment> );
Where dt is the date/time/datetime value returned,
INTERVAL is a time interval (WEEK, MONTH, HOUR, etc),
dateTime is a SAS date/time/datetime value,
increment is a positive or negative integer which specifies the number of intervals to shift the value,
and alignment controls the position of the shifted value within the interval (BEGINNING|MIDDLE|END|SAMEDAY). Default is beginning.

Got it? How about an example:

data _null_;
  * take todays date and shift it forward two months;
  thisDay = today();
  forward2Months = intnx('MONTH', thisDay, 2, 'SAMEDAY');
  put forward2Months= mmddyy10.;
run;

We specified SAMEDAY as the fourth argument instead of letting it default to BEGINNING which would have given us a date of 12/01/2005 instead of 12/07/2005.

Ready to test out your new function? I've always been confused about what day is the first day of the week? A quick google search gets me a very infomative page which states:

The Bible clearly makes the Sabbath the last day of the week, but does not share how that corresponds to our 7 day week. Yet through extra-biblical sources it is possible to determine that the Sabbath at the time of Christ corresponds to our current 'Saturday.' Therefore it is common Jewish and Christian practice to regard Sunday as the first day of the week (as is also evident from the Portuguese names for the week days). However, the fact that, for example, Russian uses the name "second" for Tuesday, indicates that some nations regard Monday as the first day.

In international standard ISO-8601 the International Organization for Standardization (ISO) has decreed that Monday shall be the first day of the week.

So for you SAS trivia buffs out there, figure out which day SAS considers to be the first day of the week. Does it follow the Judeo-Christian standard of Sunday? Or bend to the ISO-8601 standard of Monday?

Happy Friday!

A Word Counting Function For SAS

After some tinkering and toying around, I was finally able to negotiate the programming obstacle course known as SAS/TOOLKIT(R). SAS/TOOLKIT allows you to create user-written procedures, formats, informats and functions for the SAS system. I stuck to just writing a function.

The function is written in C and compiles to a dll file that you put into a SAS -PATH directory. Then you can use it just like any base SAS function. You do not need to have SAS/TOOLKIT in order to use the compiled dll file. So feel free to download the dll and use the function.

The dll file is hosted on my company site pelicanprogramming.com at
http://www.pelicanprogramming.com/sas/wcount.zip

Save the dll file after you download the zip. You can either save it to one of your SAS -PATH directories or update your SAS config file. If you don't know how to (or don't feel comfortable) updating your SAS config file, just save the dll file to
C:\Program Files\SAS\SAS 9.1\core\sasexeThis is where SAS finds most of it's own modules so adding this one in shouln't hurt anything. ;)

Oh yeah, it only works with SAS 9.13 on Windows PC SAS. Sorry SAS 8ers. Sorry Unixers.

The function is named wcount() and it counts the number of words in a string. The syntax is:

int = wcount( string <,char> );

Where int is the number of words,
string is the character string you are counting the words in,
and char is an optional second argument to specify the word delimiter. The default delimiter is a space. Actually wcount() defines a space as any "white" space: space, tab, carriage-return, newline, vertical tab and form-feed.

An example:

data _null_;
  wordCount = wCount('this  is my   test string ');
  put wordCount=;
run;

This would replace the following traditional SAS code:

data _null_;
  * count the number of words in a string;
  string = "this is my string of words";
  wordCount = 1;
  do while ( scan( string, wordCount) ^= '');
    wordCount+1;
  end;
  wordCount+(-1);
  put wordCount=;
run;

So, if you've got version 9 PC SAS and don't mind messing around a little bit, download the file and test it out. If you have any specific problems you can find my e-mail address in the readMe file included in the zip.