Date:         Fri, 15 Mar 2002 10:50:02 +0100
Reply-To:     Jim Groeneveld <J.Groeneveld@ITGROUPS.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Jim Groeneveld <J.Groeneveld@ITGROUPS.COM>
Subject:      Re: "negative" LAG
Comments: To: Daniele Monzali <Daniele.Monzali@PROMETEIA.IT>
Content-Type: text/plain

Hi Daniela,

Yes, there is. Consider the following example:

DATA TestData;
  INPUT V1 @@;
  CARDS;
1 2 3 4 5
;
RUN;

DATA TestData;
  MERGE TestData TestData (FIRSTOBS=2 RENAME=(V1=V2)); * in current order,
no BY;
RUN;

PROC PRINT DATA=TestData; RUN;

Is it clear how it works or is some explanation necessary?

Regards - Jim.
--
Y. (Jim) Groeneveld, MSc      IMRO TRAMARKO       tel. +31 412 407 070
senior statistician,          P.O. Box 1          fax. +31 412 407 080
senior data manager           5350 AA BERGHEM     IMRO TRAMARKO: a CRO
J.Groeneveld@ITGroups.com     the Netherlands     in clinical research

My computer beeps when it complains; I complain when it beeps

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> -----Original Message-----
> From: Daniele Monzali [SMTP:Daniele.Monzali@PROMETEIA.IT]
> Sent: Friday, March 15, 2002 10:26 AM
> To:   SAS-L@LISTSERV.UGA.EDU
> Subject:      "negative" LAG
>
> hello
> i have the problem of adding to a SAS dataset a "negatively" lagged value
> for a variabile, ie
>
> V1 V2
> 1    2
> 2    3
> 3    4
> 4    .
>
> my utterly inefficient solutions just consists in
>
> data out;
>  set in ; n=_n_;
> run;
> proc sort; by descending n; run;
> data out; set out; v2=lag(v1); run;
> proc sort; by n; run;
>
> cna anyone offer a more efficient solution ?
> thanks a lot
> daniele