comparison of data

[Lars Schylberg]

In addition to the anwser I gave this morning I came to think about
that I wrote a script a couple of days ago that is something in line 
with what your question was.  This script goes a little longer and
makes a segmentation to determine how many places that the changes have
occured also.  This script uses gawk since my version of
awk couldn't handle multiple arrays.

Lars

Lars Schylberg                          Email: larss at fmi.kth.se  
Dept. of Geodesy and Photogrammetry 
Royal Institute of Technology (KTH)     Tel.   +46 8 790 86 33   
S-100 44  STOCKHOLM, SWEDEN             Fax.   +46 8 790 66 10


#!/bin/sh
#
#  simp.diff.sh
#
#  Script to calculate object statistics about difference in
#  area objects that are generalized from original map to result map
#
#  Author: Lars Schylberg ( larss at fmi.kth.se )
#          Department of Photogrammetry
#          Royal Inst. of Technolgy
#          Stockholm, Sweden
#
#  Date: 930320
#  History of changes: 
#
#--------------------------------------------------------------------------
#					Check if GRASS is running
#
test "$GISRC" || echo "GRASS is not running" || exit 2
#----------------------------------------------------------------------------
#
#					Evaluate arguments
#
if [ $# != 2 ]
then
    echo
    echo Usage: `basename $0` 
    echo '       original=mapname '
    echo '       result=mapname '
    echo
    exit 1
fi
#
# 					Parse input arguments
#
for i do
	case $i in
		original*)
			ORIG=`echo $i | sed s/original=//` ;;
		orig*)
			ORIG=`echo $i | sed s/orig=//` ;;
		o*)
			ORIG=`echo $i | sed s/o=//` ;;
		result=*)
			RESU=`echo $i | sed s/result=//` ;;
		resu=*)
			RESU=`echo $i | sed s/resu=//` ;;
		res=*)
			RESU=`echo $i | sed s/res=//` ;;
		r=*)
			RESU=`echo $i | sed s/r=//` ;;
		*)
			echo ""
			echo "Unrecognized option: $i"
			echo 'Options: original=mapname '
			echo '         result=mapname '
                        echo 
			exit 1
	esac
done
#-----------------------------------------------------------------------

#					Check the input arguments

eval `g.findfile element=cell file=$ORIG`
if [ ! "$file" ] ; then
   echo "$ORIG - cell file not found"
   exit 2
fi
eval `g.findfile element=cell file=$RESU`
if [ ! "$file" ] ; then
   echo "$RESU - cell file not found"
   exit 2
fi

#-----------------------------------------------------------------------

echo "diff = if ( $ORIG != $RESU )" | r.mapcalc 2>/dev/null >/dev/null

r.clump -q i=diff o=diff.cl 2>/dev/null >/dev/null

echo ""
echo "Simplification statistics on file: $RESU"
echo ""

echo "Simpfication changes"
echo "(Number of changes : orig cat -> simp cat : cells)"

r.stats -czq i=diff.cl,$ORIG,$RESU | \
   gawk '$1 != 0 { a[$2,$3]++; s[$2,$3] += $4 } 
   END { for ( k in a ) print a[k], k, s[k] } ' 

g.remove rast=diff,diff.cl >/dev/null

echo ""
echo "Original Category Statistics"
echo ""

r.stats -qzc i=$ORIG

echo ""
echo "Simplification Category Statistics"
echo ""
r.stats -qzc i=$RESU