set ytics 0,500 plot "bg.gnu" index 0:0 using 1:2 w p, "bg.gnu" index 1:1 using 1:2 w l,"top.gnu" index 0:0 using 1:2 w p,"top.gnu" index 1:1 using 1:2 w l,"peak.gnu" index 0:0 using 1:2 w p,"peak.gnu" index 1:1 using 1:2 w l, "peak.gnu" index 2:2 using 1:2 w l