http://gnuplot.info/

$ sudo apt-get install gnuplot
	

$ cat test.log
8:00 506.877
8:30 501.068
9:00 493.254
9:30 469.184
10:00 460.161
11:00 426.065
12:00 429.734
14:00 409.255
15:00 423.512
16:00 390.676
17:00 390.676
18:00 390.676

$ cat test.gnuplot
set terminal png truecolor size 800,250
set output "test.png"
set autoscale
set xdata time
set timefmt "%H:%M"
set style data lines
set xlabel "time per day"
set ylabel "Mbps"
set title "Apache Traffic"
set grid
plot "test.log" using 1:2 title "Hit"

$ gnuplot test.gnuplot
	

set terminal png

set terminal png truecolor size 800,600
set output "asa5550.png"