Date:         Wed, 6 Feb 2002 00:21:34 +0100
Reply-To:     Peter Crawford <peter.crawford@DB.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Peter Crawford <peter.crawford@DB.COM>
Subject:      Re: Missing values for character variables
Comments: cc: John Whittington <John.W@mediscience.co.uk>
Content-type: text/plain; charset=iso-8859-1

I would like to re-but what John refers as
"In theory, yes - but there are obvious problems"

SI had obvious problems introducing the "alien" concept of missing
values in the first (numeric) place.
But they did - and created many good data management
opportunities with the concept.

Import of non-printable character values is no different from import
of anything else - subject to chosen or defaulted informats.

Presentation of the "unprintable" character special missing values
could be subject to handling similar to numeric special missings
and we can make whatever formats we want.(probably)

The missing statement (not option) could/should be able to be
extended for special character missings.

For those customers with no use for special character missing,
there need be no impact.

On an update statement there are special rules for updating
variables to "missing" but that cannot apply to character missing
... while there is no special character missing.

I think character special missings would add value.

Regards
Peter Carwford




Datum:         06.02.2002 00:04
An:            Peter Crawford/Zentrale/DeuBaExt@Zentrale
               SAS-L@LISTSERV.UGA.EDU



Betreff:       Re: Missing values for character variables
Nachrichtentext:

At 23:56 05/02/02 +0100, Peter Crawford wrote (in part):

>It seemed almost too easy for SI to choose the characters for
>the line drawing in sasfont '82'x --'8C'x  (especially when there
>already existed ms-linedraw and oem fonts offering another standard.
>
>So it would seem reasonable for SI to choose some "unprintable" characters
>as special missing character values .....the "characters" with hex values
>below blank are a set of candidates

In theory, yes - but there are obvious problems associated with using
'unprintable' characters for this purpose, precisely because they do not
'print' (or have a predictable, cross-platform and cross-applications,
effect on what appears on screen or paper) - particularly when one realises
that a high proportion of variable values originate from outside of SAS.

Kind Regards


John

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