Murlidhar Fichadia Murlidhar Fichadia - 5 months ago 30
Bash Question

Min-Max Normalization using AWK

I dont know Why I am unable to loop through all the records. currently it goes for last record and prints the normalization for it.

Normalization formula:



New_Value = (value - min[i]) / (max[i] - min[i])

Program



{
for(i = 1; i <= NF; i++)
{
if (min[i]==""){ min[i]=$i;} #initialise min
if (max[i]==""){ max[i]=$i;} #initialise max
if ($i<min[i]) { min[i]=$i;} #new min
if ($i>max[i]) { max[i]=$i;} #new max
}

}
END {
for(j = 1; j <= NF; j++)
{
normalized_value[j] = ($j - min[j])/(max[j] - min[j]);
print $j, normalized_value[j];
}
}


Dataset



4 14 24 34
3 13 23 33
1 11 21 31
2 12 22 32
5 15 25 35


Current Output



5 1
15 1
25 1
35 1


Required Output



0.75 0.75 0.75 0.75
0.50 0.50 0.50 0.50
0.00 0.00 0.00 0.00
0.25 0.25 0.25 0.25
1.00 1.00 1.00 1.00

Answer

I would process the file twice, once to determine the minima/maxima, once to calculate the normalized values:

awk '
    NR==1 {
        for (i=1; i<=NF; i++) {
            min[i]=$i
            max[i]=$i
        }
        next
    }
    NR==FNR {
        for (i=1; i<=NF; i++) {
            if      ($i < min[i]) {min[i]=$i}
            else if ($i > max[i]) {max[i]=$i}
        }
        next
    }
    {
        for (i=1; i<=NF; i++) printf "%.2f%s", ($i-min[i])/(max[i]-min[i]), FS
        print ""
    }
' file file
# ^^^^ ^^^^  same file twice!

outputs

0.75 0.75 0.75 0.75 
0.50 0.50 0.50 0.50 
0.00 0.00 0.00 0.00 
0.25 0.25 0.25 0.25 
1.00 1.00 1.00 1.00