Shell Programming and Scripting

site val1 val2
002 10 25.3
002 20 25.3
002 30 25.3
002 40 20
002 50 20
002 60 20
002 70 20
002 80 30
002 90 30
002 100 30
002 120 30
003 20 30.3
003 20 30.3
003 30 20
003 40 40

awk '
        NR > 1 {
                ++T[$1]
                A[$1 FS T[$1]] = $2
        }
        END {
                print "Site", "Val"
                for ( k in T )
                {
                        idx = sprintf( "%.0f", T[k] * 0.05 )
                        idx = ( idx == 0 ? 1 : idx )
                        print k, A[k FS idx]
                }
        }
' OFS='\t' file