set xdata time
set timefmt "%Y:%m:%d:%H:%M:%S"
set style data lines
set format x "%H:%M"
set term png size 1100,600
set output 'example4.png'
f='example4.data'
plot [] [0:120] f using 1:2 title 'USER+NICE', f using 1:3 title 'disk:KB(44616)', f using 1:4 title 'net:WKB(43836)'