Date:         Wed, 30 Jul 2008 13:25:21 -0400
Reply-To:     Muthia Kachirayan <muthia.kachirayan@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Muthia Kachirayan <muthia.kachirayan@GMAIL.COM>
Subject:      Re: current minus previous value/another approach with SAS?
In-Reply-To:  <200807301622.m6UB5H9C021452@malibu.cc.uga.edu>
Content-Type: text/plain; charset=WINDOWS-1252

On Wed, Jul 30, 2008 at 12:22 PM, KNuak <asom77@hotmail.com> wrote:

> Hello,
> Does anyone know of any other method (apart from the dif and the ifn
> functions) to find
> Current minus previous values?
> I have dataset1 below and calculated dht= differences in ht(ie.current –
> previous) and dawk=differences in awk(ie. current minus previous) all by
> id below and obtained the results(output) in dataset2 below, using the ifn
> and the dif functions.
> *I want another approach to address the problem. Ie. an alternative
> method, not using the ifn and the dif functions.
> ANY ADVICE, PLEASE ON USING A DIFFERENT SAS CODE, instead of the ifn and
> the dif functions.
>  used the following SAS code to obtain the output in dataset2:
> Data b;
> Set a; /*a contains dataset1*/
> By id;
> Dht=ifn(first.id,(.), dif(ht));
> Dawk=ifn(first.id,(.),dif(awk));
> Run;
>
> Dataset1:
>  id        awk       ht
>  29      4.3607     188
>  29      7.1803     310
>  29      9.9672     355
>  31      2.0656     112
>  31      3.1148     156
>
>
>
> Dataset 2:
>  id     awk     ht     dht   dawk
>  29   4.3607   188     .      .
>  29   7.1803    310   122   2.81967
>  29   9.9672    355    45   2.78689
>  31   2.0656    112    .       .
>  31   3.1148    156    44  1.04918
>

Wondering why you do not want those functions?

Store the values to some temporary variables and use it for finding
differences.

data need;
do until(last.id);
   set have;
   by id;
   if first.id then do; prev_awk = awk; prev_ht = ht; end;
   else do; dht = ht - prev_ht; dawk = awk - prev_awk; end;
   output;
end;
drop prev:;
run;

Muthia Kachirayan