Date:         Tue, 7 Oct 2008 19:07:46 -0400
Reply-To:     "Howard Schreier <hs AT dc-sug DOT org>"
              <schreier.junk.mail@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Howard Schreier <hs AT dc-sug DOT org>"
              <schreier.junk.mail@GMAIL.COM>
Subject:      Re: Missing variables

On Mon, 6 Oct 2008 20:23:56 -0400, Lou <lpogoda@HOTMAIL.COM> wrote:

>Randy wrote:
>> Dear All:
>> My data is as follows
>>
>> varID
>> 1
>> 2
>> 3
>> 4
>> 0
>> 7
>> 8
>> 0
>> 10
>> 11
>> 12
>> 0
>> 16
>> and so on
>> I need to construct another var, VARID_one
>> where
>> varid    varid_one
>> 1         1
>> 2         2
>> 3         3
>> 4         4
>> 0         6
>> 7         7
>> 8         8
>> 0         9
>> 10        10
>> 11        11
>> 12        12
>> 0         15
>> 16        16
>> Where the when the value of VarID = 0 then VarID_one = the next value of
>> VarID - 1.
>>                 Randy
>Assuming your data are in a dataset called VARIDS, a simple merge will
>get you where you want to go:
>
>data result (drop = nextid);
>
>    merge varids
>
>          varids (firstobs = 2
>
>                  rename = (varid = nextid));
>
>    if varid = 0 then varid_one = nextid - 1;
>
>    else varid_one = varid;
>
>run;
>
>Caution - the final value of NEXTID will be missing, so if the final
>value of VARID is 0, then the final value of VARID_ONE will be missing
>minus one - in other words, missing.

A slightly terser variation:

   data result;
   merge varids
         varids( firstobs = 2 rename = (varid = varid_one) );
   varid_one = ifn( varid = 0 , varid_one - 1 , varid);
   run;