Default DATA Step Behavior Without a RETAIN statement, SAS automatically sets variables that are assigned values by an INPUT or assignment statement to missing before each iteration of the DATA step.

Assigning Initial Values Use a RETAIN statement to specify initial values for individual variables, a list of variables, or members of an array. If a value appears in a RETAIN statement, variables that appear before it in the list are set to that value initially. (If you assign different initial values to the same variable by naming it more than once in a RETAIN statement, SAS uses the last value.) You can also use RETAIN to assign an initial value other than the default value of 0 to a variable whose value is assigned by a sum statement.

Redundancy It is redundant to name any of these items in a RETAIN statement, because their values are automatically retained from one iteration of the DATA step to the next:

variables that are read with a SET, MERGE, MODIFY or UPDATE statement

a variable whose value is assigned in a sum statement

the automatic variables _N_, _ERROR_, _I_, _CMD_, and _MSG_

variables that are created by the END= or IN= option in the SET, MERGE, MODIFY, or UPDATE statement or by options that create variables in the FILE and INFILE statements

data elements that are specified in a temporary array

array elements that are initialized in the ARRAY statement

elements of an array that have assigned initial values to any or all of the elements on the ARRAY statement.

You can, however, use a RETAIN statement to assign an initial value to any of the previous items, with the exception of _N_ and _ERROR_.

Toby Dunn

From: John McQuown <John.McQuown@OTNNET.COM> Reply-To: John McQuown <John.McQuown@OTNNET.COM> To: SAS-L@LISTSERV.UGA.EDU Subject: Re: SUSPECT: Re: Retain Date: Wed, 2 Mar 2005 20:15:00 -0800

Strange that no one has mentioned that arrays, when initialized or temporary, are automatically retained... A stealth RETAIN.

Cheers, john

-----Original Message----- From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of toby dunn Sent: Wednesday, March 02, 2005 7:35 PM To: SAS-L@LISTSERV.UGA.EDU Subject: SUSPECT: Re: Retain

Okay I have but my tongue long enough on where this thread is going:

Two things:

The retain statement does not, cannot, and will not (as long as the underlying code is written currently) retain a thing. Nor will it create a counter or accumulator variable, nor will it create a lag variable. The retain function will stop the SAS supervisor from resetting certain variables stated in the retain statement from being reset to missing with each iteratoin of the data step. Now one can use the retain statement with other coding techniques or functions to create variables that effectively act like a accumulator, count, or lag variable.

The lag function doesn't even perform a true lag, it merely creates teh illusion of a lag variable.

Why is this so important to get straight, well not knowing what the retian statement or lag function does has lead more programmers down the path of insanity and baldness than probrably any other topic in SAS other than maybe Ian's macro design or Pauls hash programs. once one knows how they do what they do, then one can use them to their advantage.

Toby Dunn

From: Frank Berger <frank.d.berger@DAL.FRB.ORG> Reply-To: Frank Berger <frank.d.berger@DAL.FRB.ORG> To: SAS-L@LISTSERV.UGA.EDU Subject: Re: Retain Date: Wed, 2 Mar 2005 16:41:31 -0600

"Grado" <grado2005@gamespy.com> wrote in message news:FgqVd.1078$WC1.1055@tornado.fastwebnet.it... > > "Stat" <stat@upenn.edu> ha scritto nel messaggio > news:d057sp$7l7j$1@netnews.upenn.edu... > > Hi, > > > > What are your top 5 reasons for using the RETAIN function? > > > > - SH > > > > 1) to count or cumulate something in a datastep > 2) to arrange variables order in a dataset > > are you carrying out a market research on the topic? > > 3. To create a constant. 4. To create a lag variable without using the lag function. As in:

data temp2; retain lx; set temp1 (keep=x); if _n_ ne 1 then if x ne lx then output; lx=x; run;