Date:         Thu, 2 Jul 2009 06:30:38 -0700
Reply-To:     smolkatz <smolkatz@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         smolkatz <smolkatz@GMAIL.COM>
Organization: http://groups.google.com
Subject:      Re: how to lag in panel
Comments: To: sas-l@uga.edu
Content-Type: text/plain; charset=ISO-8859-1

On Jul 2, 2:39 pm, ilann...@GMAIL.COM (Liang Xu) wrote:
> Hi,guys. I have an unbalanced panel data, and I need to lag some variables.
>
> name time value                name time value
> a     1     20                   a    1     .
> a     2     30                   a    2     20
> a     3     40                   a    3     30
> b     1     22       to          b    1     .
> b     2     33                   b    2     22
> b     3     44                   b    3     33
>
> It looks that the example above. My problem is how to deal with the value of
> b at time 1 when I lag b once?
> And if I want to lag b twice, how can I do it?
> Thanks!

Hi,
if you want to lag every name only once as you show in then example
than this could be the answer:

data a;
input name $ time value;
cards;
a     1     20
a     2     30
a     3     40
b     1     22
b     2     33
b     3     44
;

proc sort data=a;
by name time;
run;

data b;
set a;
 by name;
value=lag(value);
if first.name then value=.;
run;

Alexandra