Base SAS Tip Sheets on support.sas.com

Very useful reference sheet.
Hope SAS provide more tip sheets. :)

For more information, click here

Replacing a string in a file

Generally, there are two types to replace string in a file.
Classic type: infile / file
C type: functions for external files (fopen, fread, fwrite etc)

Here I want to give two points:
#1:
Classic type can not do in-place update. That means we have to creat a new file.
Note that with SHAREBUFFERS option in infile statement, we can also do in-place update.

#2:
Although C type can do in-place update, string to write can NOT be longer than the string to read.

The two examples at below are helpful.
Classic type:
http://www.sconsig.com/sastips/tip00327.htm
C type:
http://support.sas.com/kb/32/868.html

USER system option for batch mode debug

We run SAS program in two mode: batch mode and interactive mode (DMS/NODMS).

With batch mode, I can automate and schedule the SAS job. This can improve the work efficiency dramatically.
However, when SAS job fail, it will take more time to solve the issue.

Below are the steps:
1. With system option USER, run the file and save WORK datasets in permanent libary.
2. Check the error point in SAS log.
3. Start from error point, debug the code step by step.

Interval: Key concept to INTNX and INTCX

When handling dates and times, we must know two powerful functions: INTNK and INTCK.
The two functions are complementary.
INTNK is for new date value incremented by a specified number of intervals, while INTCK for the number of intervals between two dates.

It is hard for a fresh SAS programmer to understand the two functions because they are not intuitive.
However, as a qualified SAS programmer, it should be a must.

Actually, the key concept behind the two functions is INTERVAL.
If you get it, anything will be simple.

INTNX Demo:
INTNX("year", "31Dec2000"d, 2);

As to "Year" interval, "31Dec2000"d is in the interval between "01Jan2000"d and "31Dec2000"d.
So the new interval should be calculated as follow:
"01Jan2000"d and "31Dec2000"d
+
2
= "01Jan2002"d and "31Dec2002"d.
In the new interval, INTNX return date ‘01Jan2002’d. (Note: the default alignment is beginning).

INTCK Demo:
INTCK("year","31Dec2000"d, "01Jan2001"d);
As to ‘Year’ interval, '31Dec2000'd is in the interval between "01Jan2000"d and "31Dec2000"d’,
While "01Jan2001"d in the interval between "01Jan2001"d and "31Dec2001"d

The number of interval is:
"01Jan2001"d and "31Dec2001"d
-
"01Jan2000"d and "31Dec2000"d’
= 1

So INTCX return number 1.


One more thing:
SAS always focus on improvement of "The Power to DO". (I have modified the logo. Wow.)
With new introduction of alignment value ‘sameday’ in INTNK in SAS 9, many old solutions will step off the stage of history.

DO NOT use IFN in division by Zero

IFN is a compact format for IF/THEN/ELSE. However, it runs with a different manner.

In IFN, all expressions will be evaluated at first. And then logical judgement will be applied and regarding value be returned, while IF/THEN/ELSE need not evaluate all expressions.

data test1;
    input a b ;
    l=ifn(b>0 , 0 , a/b ); 
* 'b>0' and 'a/b' will be evaluated, so error occur;
cards;
10 2
6 0
9 3
;

data test2;
    input a b;
    if b=0 then l=0;
    else l=a/b;
cards;
10 2
6 0
9 3
;

How to sort dataset with format?

Every SAS programmer must be familiar with Proc SORT. Every time we merge multiple datasets, do group-by processing, etc. we have to sort the dataset by key variables.

In many procs, Format statement can function partly as group-by processing, e.g. Proc MEANS, Proc REPORT etc.

However, different from the procs above, Format statement dose not do group-by processing in Proc SORT.
The Format statement in Proc SORT ONLY assign the format to the variable in output dataset.

Generally, we create a new variable based on the format and then sort the new variable using Proc SORT.
With Proc SQL, we can do the same operations in one step. :)

Sample code:

proc format;
value $sex
  'M' = '1'
  'F' = '2';
run;

* Format statement does not work in Proc SORT;
proc sort data=sashelp.class out=sortfail;
 format sex $sex.;
 by sex;
run;

* With Proc SQL, we can sort the dataset with format
 in one step;
proc sql;
 create table sortok as
  select * from sashelp.class
  order by put(sex, $sex.);
quit;

* More steps with "by vars NOTSORTED";

Execute code on the fly

Do you want to execute code on the fly?

There are two methods:
1. call execute routine
2. temp file + %include

filename test temp;
data _null_;
filename test;
**** put code here ****;
run;
%include test;

The latter method is more popular and friendly.