mirror values at edges

GRASS GIS GRASS GIS developer
1

I started to write a script to determine neighbours for each clump in
a map. I came up with a solution were I mirror the values at all edges.

My question now is if this could be written in one r.mapcalc statement
directly, instead of these four r.mapcalc and the r.patch statement ?

I have been trying with several versions of nested if and eval statements,
but I have found no solution.

This is the script that I came up with.

---------------------------------------------------------------------
#!/bin/sh
#
# $1 = first argument which should be a cell file

CLUM=$1

echo "temp1 = if( $CLUM != $CLUM[0,1], $CLUM[0,1], 0)" | r.mapcalc
echo "temp2 = if( $CLUM != $CLUM[1,0], $CLUM[1,0], 0)" | r.mapcalc
echo "temp3 = if( $CLUM != $CLUM[0,-1], $CLUM[0,-1], 0)" | r.mapcalc
echo "temp4 = if( $CLUM != $CLUM[-1,0], $CLUM[-1,0], 0)" | r.mapcalc

r.patch i=temp1,temp2,temp3,temp4 o=edge.mirror
----------------------------------------------------------------------

Lars

Lars Schylberg Email: larss@fmi.kth.se
Department of Photogrammetry
Royal Institute of Technology Tel. +46 8 790 86 33
S-100 44 STOCKHOLM, SWEDEN Fax. +46 8 790 66 10

2

This is a reply to my own question. After a good nights sleep it was all
obvious to me.

r.mapcalc << EOF
neigh.mirror=eval( t1 = if( $CLUM != $CLUM[0,1], $CLUM[0,1], 0), \\
                   t2 = if( $CLUM != $CLUM[1,0], $CLUM[1,0], 0), \\
                   t3 = if( $CLUM != $CLUM[0,-1], $CLUM[0,-1], 0), \\
                   t4 = if( $CLUM != $CLUM[-1,0], $CLUM[-1,0], 0), \\
                   max( t1, t2, t3, t4 ))
EOF
--------

Lars

Lars Schylberg Email: larss@fmi.kth.se
Department of Photogrammetry
Royal Institute of Technology Tel. +46 8 790 86 33
S-100 44 STOCKHOLM, SWEDEN Fax. +46 8 790 66 10