# {{{ ->create graph method
    # 
    sub create_graph {
        my $class = shift;

        open my $plot => "| /usr/local/bin/gnuplot" 
            or die "Failed to open pipe: $!\n";

        my $outfile = "/tmp/graph.png";
        print $plot <<"        --";
        set  terminal png color
        set  out "$outfile"
        set  format x "/%b%y/"
        set  xdata  time
        set  key left top Left reverse samplen 2 title "Legend" box
       
        set  timefmt "%s:"

        set  grid   xtics ytics
        set  xtics  nomirror
        set  ytics  nomirror
        set  y3tics nomirror

        set  autoscale

        set  ylabel "ResponseTime"
        plot "$_[0]" using 1:2 smooth unique axis x1y1 title "Time in ms"
        --
        #set   timefmt "%Y-%m-%d:"
        close $plot or die "Failed to close pipe: $!\n";
        chmod 0644 => $outfile or die "Failed to chmod $outfile: $!\n";

    } # }}}