Gnuplot

From LinuxIntro
Jump to: navigation, search

Contents

OverView

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

vmstat 1 10 | grep -v r > vmstat.txt
gnuplot -p -e "plot 'vmstat.txt' using 13 title 'CPU user load' with lines, 'vmstat.txt' using 14 title 'CPU system load' with lines, \
'vmstat.txt' using 15 title 'CPU idle time' with lines, 'vmstat.txt' using 16 title 'CPU IO wait time' with lines"

The result will look like this:

Snapshot-gnuplot.png

xy diagrams

lines

Maybe you do not have data for every x value. Let's say you want to plot your weight and have measured your weight on monday, tuesday and friday, but not on wednesday and thursday. In this case you must tell gnuplot as well the X as the Y coordinate of every measurement. You want a graph like this:

Snapshot-gnuplot-weight.png

The above has been taken with the command

gnuplot -p -e "plot 'weight' using 1:2 with linespoints"

and the data in the file weight:

1 90
2 93
4 95
7 94
8 93
10 94

bars

Or maybe you get data from your serial port showing voltage levels for transmitting characters as to be seen on wikipedia. In this case you want a chart with bars like this:

Snapshot-gnuplot-bars-wxt.png

It has been drawn with the command

 gnuplot -p -e "set terminal wxt size 400,200; set yrange[-0.5:1.5]; set style fill solid; plot 'csv.csv' using 1:2 with boxes"

on the data in csv.csv (time vs bit level):

2.919770956 1
2.9377708435 0
2.9438738823 1
3.0778059959 0
3.0837988854 1
3.0907878876 0
[...]

Output to a file

To save your output as a .png file, add the commands below in bold:

gnuplot -p -e "plot 'datasource.txt' using 4  with lines;set output 'test.png';set terminal png;replot"

TroubleShooting

If you get an error message like

gnuplot -p -e "plot 'data.txt' with lines"
Cannot open load file '-p'
line 0: util.c: No such file or directory

You are most probably on an outdated gnuplot version. Version 4.4 differs a lot from 4.2.

See also

  • ksar
  • dot : Create graphics using text commands