Date:         Tue, 22 Sep 1998 12:48:04 -0500
Reply-To:     lloschky@s.psych.uiuc.edu
Sender:       "SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU>
From:         Lester Loschky <lloschky@S.PSYCH.UIUC.EDU>
Organization: Psychology
Subject:      Re: Lag vs. Lead functions: Problem is solved! :)
Content-Type: multipart/alternative;

Thanks to everyone who sent helpful suggestions for how to solve the lag
vs. lead function problem!  I have been able to successfully implement a
solution and it worked perfectly!  Several people (Ed Tverdek being the
first) suggested the following approach (quoted from a message from
David Matheson):
 
 
> 2. Create a variable that is equal to the case number and sort the file
>     in descending order on that variable.  Use the lag function to compute
>    your new variable. Resort the file to the original order.
>
> compute seq = $casenum.
> sort cases by seq (d) .
> do if (lag(subject) = subject and lag(trial) = trial) .
> compute fixdrld = lag(fixdur).
> end if.
> execute.
> sort cases by seq.
>
>
> David Matheson
> SPSS Technical Support
>
 
Thanks again for everyone's help!
 
 
Lester
**************
 
Lester Loschky
Human Perception and Performance Group
Beckman Institute for Advanced Science and Technology
405 North Mathews
Urbana, IL  61801
E-mail: loschky@s.psych.uiuc.edu
Phone/voice-mail: 217-333-0970
 
 
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