Date:         Mon, 18 May 2009 04:21:31 -0700
Reply-To:     "Schwarz, Barry A" <barry.a.schwarz@BOEING.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Schwarz, Barry A" <barry.a.schwarz@BOEING.COM>
Subject:      Re: Flagging multiple ID's on the same day
In-Reply-To:  <5919cff3-490e-44c5-abf0-17d032bf3484@o27g2000vbd.googlegroups.com>
Content-Type: text/plain; charset="us-ascii"

Your comment would be correct if the expression were (first.ID_B =
last.ID_B).

As written, the expression is true only for a group with a single
observation.

With a multi-observation group, last.ID_B is 0 for the first observation
(rendering the entire expression false) and first.ID_B is 0 for every
subsequent observation (also rendering the entire expression false).

-----Original Message-----
From: Richard A. DeVenezia
Sent: Monday, May 11, 2009 5:21 AM
To: SAS-L@LISTSERV.UGA.EDU
Subject: Re: Flagging multiple ID's on the same day

snip

Additionally, (first.ID_B and last.ID_B) is an insufficient test

(first.ID_B and last.ID_B) will test true in two different situations
- single observation in group (flags are both 1)
- more than 2 observations in group, and at an 'internal' observation
(flags are both 0)