cat file for r.mapcalc

From grass-lists-owner@moon.cecer.army.mil Fri Oct 13 16:20:07 1995
Sender: grass-lists-owner@moon.cecer.army.mil
Reply-To: grassu-list@moon.cecer.army.mil
To: info-grass-user@uunet.uu.net
Path: access1!zhuang
From: zhuang@access.digex.net (Xin Zhuang)
Newsgroups: info.grass.user
Subject: cat file for r.mapcalc
Date: 13 Oct 1995 16:46:30 -0400
Organization: Express Access Online Communications, Greenbelt, MD USA
Lines: 30
Keywords: cats, r.mapcalc
Content-Length: 431

I have two layers: left and right. They don't overlay.
I'd like to merge them together. Guess I can use
either
  new = left + right
or more safely
  new=if(left,left,right)

However, there won't be category contents for Layer "new".
Is there a way to bring category contents in Layers "left"
and "right" into Layer "new"?
Or maybe I should use another function?

Appreciate any hint and help.

zhuang@access.digex.net

Have you looked at r.patch?

Bill Jackson
LL-N
USACERL