set term png small color
set data style lines
set grid
set yrange [ 0 : ]
set title "Traffic in last XX hours"
set xlabel "hours"
set ylabel "kBytes"
set multiplot
plot "in.txt" using ($1/3600):($2/1000) title "IN Traffic" with linespoints, "out.txt" using ($1/3600):($2/1000) title "OUT Traffic" with linespoints