Ron Cody

7月 252019
 

Years ago I saw a line of SAS code that was really puzzling. It was a statement that started with:

if 0 then … ;

What? This was a statement that would always be evaluated as false. Why would anyone write such a statement? Recently, I was discussing with a good friend of mine a macro I wrote where I used an IF statement that was always false.

DATA Step compiler shortcut
In some programming languages, the "IF 0" trick ensures that the code that follows would never be executed.  But with the DATA step, SAS actually does still evaluate the "zeroed-out" code during the compile phase.

Let's see why this can actually be useful.

The problem I was trying to solve was to assign the number of observations in a data set to a macro variable. First, the code, then the explanation.

if 0 then set Oscar Nobs=Number_of_Obs; call symputx('Number',Number_of_Obs); stop; run;

The SET option Nobs= places the number of observations in data set Oscar in a variable I called Number_of_Obs. This happens at compile time, before any observations are read from data set Oscar. The CALL SYMPUTX routine takes two arguments. The first is the name of a macro variable (Number) and the second is the name of a SAS variable (Number_of_Obs). The call routine assigns the value of the SAS variable to the Macro variable.

Titles by Ron CodyMost data sets stop executing when you reach the end-of-file on any data set. Because you are not reading any values from data set Oscar, you need a STOP statement to prevent the Data Step from looping. When this Data Step executes, the number of observations in data set Oscar is assigned to the macro variable called Number.

Now you, too, can write programs using this useful trick. The macro where I used this trick can be found in my book, Cody's Data Cleaning techniques, 3rd edition. You can see a copy of this macro (and all the other macros described in the book) by going to my author web site: support.sas.com/cody, scrolling down to the Data Cleaning book and clicking on the link to see example and data. One of the macros that use this trick is called HighLow.sas. As an alternative, you can buy the book!

By the way, you can download programs and data from any of my books by using this same method and it is free!

Books by Ron Cody See them all!

A DATA step compiler trick to get the record count was published on SAS Users.

10月 022018
 

I often get asked for programming tips. Here, I share three of my favorite tips for beginners. Tip #1: COUNTC and CATS Functions Together The CATS function concatenates all of its arguments after it strips leading and trailing blanks. The COUNTC function counts characters. Together, they can let you operate [...]

The post Three of My Favorite Programming Tips appeared first on SAS Learning Post.

6月 272017
 

In a previous blog, I demonstrated a program and macro that could identify all numeric variables set to a specific value, such as 999. This blog discusses an immensely useful technique that allows you to perform an operation on all numeric or all character variables in a SAS data set. [...]

The post How to perform an operation on all numeric or all character variables in a SAS data set appeared first on SAS Learning Post.

6月 272017
 

When I teach my Data Cleaning course, the last topic I cover in the two-day course is SAS Integrity Constraints.  I find that most of the students, who are usually quite advanced programmers, have never heard of Integrity Constraints (abbreviated ICs).  I decided a short discussion on this topic would [...]

The post Keeping your data set clean: Integrity constraints appeared first on SAS Learning Post.

6月 062017
 

Wait!  Don't close this window.  I understand that regular expressions can be very complicated (yes, there are many books on the subject), but some basic expressions to test patterns such as zip codes or telephone numbers are not that difficult.  In addition, you can sometimes use Google to search for [...]

The post Using regular expressions to verify the pattern of character data appeared first on SAS Learning Post.

4月 012017
 

There's an old song that starts out, "You Can Get Anything You Want at Alice's Restaurant."  Well, maybe you are too young to know that song, but if you’re a SAS users, you’ll be glad to know that you can capture anything produced by any SAS procedure (even if the [...]

The post Capturing output from any procedure with an ODS OUTPUT statement appeared first on SAS Learning Post.