r.mapcalc and categories

GRASS GRASS user
1

From grass-lists-owner@max.cecer.army.mil Wed Jul 21 09:06:13 1993
From: ca4@aixfile1.urz.uni-heidelberg.de (Stefan Jaeger)
Subject: r.mapcalc and categories
Sender: grass-lists-owner@max.cecer.army.mil
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Date: Wed, 21 Jul 93 12:18:34 CET
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Hi,

I used r.mapcalc for the automated production of a classified map with about
200 categories. How can I assign category labels to those classes
without r.support or r.reclass?

Stefan Jaeger
Dept. of Geography
University of Heidelberg
Germany

To assign categories you need to append your category labels to the
$LOCATION/cats file. The first four lines will be created automatically
whether you assign labels or not. The remaining lines consist of a
series of lines of the form: #:label, where "#" is the category number
and "label" is the label assigned to that number. To automate the
labeling process you could write a script that prompts the user for
labels and then adds them to the bottom of the cats file.

You can easily incorporate the r.mapcalc along with the labeling process
in one shell script.

For example I created the executable:

#!/bin/sh

catnumber=1
while [ $catnumber ]
do
        echo "please enter the category number" > "/dev/tty"
        read catnumber < "/dev/tty"
        echo "please enter the corresponding label" > "/dev/tty"
        read label < "/dev/tty"
        echo $catnumber":"$label >> $LOCATION/cats/$1
done

It prompts the user for category numbers and labels and appends them
to the category file specified on the command line. I called the
script writecats. I prompts until receiving a null category number.
It unfortunately prints a bogus final line to the cats file consisting
of only a colon. But that can be fixed by bracketing:
        echo $catnumber":"$label >> $LOCATION/cats/$1
with an if statement.

Example of usage:

tahoe{sue}98 % writecats filename
please enter the category number
1
please enter the corresponding label
first
please enter the category number
2
please enter the corresponding label
second
please enter the category number

please enter the corresponding label

Appends the cats file "filename" to:

# 5 categories
Nine County At Risk Map

0.00 0.00 0.00 0.00
1:first
2:second
:

Good luck.
If you need more help with shell scripts email me directly.

sue huse
Univ Calif Berkeley