#!/bin/sh
# Parameters: 1, 2, 3 - number of LANDSAT band
# written by Markus Neteler 21. Jul. 1998, 5. Jan. 1999
#            neteler geog.uni-hannover.de | neteler itc.it


# submodule of i.oif
if [ $# -ne 3 ] ; then
    g.message -e "You must use i.oif instead of i.oifcalc (this is a submodule)"
    exit 1
fi

if [ "$1" -lt 1 ] || [ "$1" -gt 7 ] || [ "$2" -lt 1 ] || [ "$2" -gt 7 ] || [ "$3" -lt 1 ] || [ "$3" -gt 7 ] ; then
    g.message -e "Invalid channel combination ($1 $2 $3)"
    exit 1
fi

PROG=`basename "$0"`

#### check if we have awk
if [ ! -x "`which awk`" ] ; then
    g.message -e "awk required, please install awk or gawk first" 
    exit 1
fi

# setting environment, so that awk works properly in all languages
unset LC_ALL
LC_NUMERIC=C
export LC_NUMERIC

# calculate SUM of Stddeviations:
"$GISBASE"/etc/i.oif/m.cutmatrix "$temp_stddev" 1 "$1" >  "$temp_sum"
"$GISBASE"/etc/i.oif/m.cutmatrix "$temp_stddev" 1 "$2" >> "$temp_sum"
"$GISBASE"/etc/i.oif/m.cutmatrix "$temp_stddev" 1 "$3" >> "$temp_sum"

cat "$temp_sum" | awk \
'BEGIN {sum = 0.0} 
NR == 1{}
	{sum += $1 ; N++}
END{
print sum
}' > "$temp_calc"

# calculate SUM of absolute(Correlation values):
"$GISBASE"/etc/i.oif/m.cutmatrix "$temp_correlation" "$1" "$2" >  "$temp_sum"
"$GISBASE"/etc/i.oif/m.cutmatrix "$temp_correlation" "$1" "$3" >> "$temp_sum"
"$GISBASE"/etc/i.oif/m.cutmatrix "$temp_correlation" "$2" "$3" >> "$temp_sum"

cat "$temp_sum" | awk \
'BEGIN {sum = 0.0}
NR == 1{}
        {sum += sqrt($1*$1) ; N++}  # sqrt(x^2) is my ABS-function
END{
print sum
}' >> "$temp_calc"

# Calculate OIF index:
#     Divide (SUM of Stddeviations) and (SUM of Correlation)
cat "$temp_calc" | awk 'BEGIN {}
{count = divisor; divisor = $1;}      # value shift - no better idea ;-)
END{
print count / divisor
}'