Gnuplot

Here is an example how to visualize vmstat's output using gnuplot.

vmstat -nd 1 2 | grep -v r | awk '{print $4;}' >vmstat.txt
gnuplot -p -e "plot 'vmstat.txt' with lines"

gnuplot> plot 'vmstat.txt' using 1:4 title 'HI' with lines, \
>'vmstat.txt' using 1:5 title 'lo' with lines;

plot 'vmstat.txt' using 4 title 'free mem' with lines, 'vmstat.txt' using 5 title 'buffers' with lines, 'vmstat.txt' using 6 title 'caches' with lines