1. CSE4251 The Unix Programming Environment
Lecture 13
gnuplot

2. What is Gnuplot A portable command-line driven graphing utility
can output most of the picture formats
eps/pdf/tex: good for writing academic pictures
now added html, javascript: display data on web
Can use interactive command and script file
script is good to automate the task!

3. Interactive plot launch gnuplot: $ gnuplot $ gnuplot gnuplot>
gnuplot> plot sin(x)

4. set plot range set xrange [0:5] # define x range
set yrange [0:10] # define y range
$ gnuplot
gnuplot>
gnuplot> plot sin(x)
gnuplot > set xrange [0:5]
gnuplot > replot

5. plot from script Save plot commands in file, and run gnuplot:
$ gnuplot mycmds.plt
Output disappears quickly; use pause to see the result, e.g.:
plot sin(x)
pause -1 "Hit any key to continue“

6. commonly used commands
help topic #get help about a topic
replot #repeat last plot command
clear #remove objects in the canvas
set OPTION [VALUE] #specify plot options
set xrange [0:5] #set the horizontal axis range
set multiplot #several plots on the same figure
show [all] # show (all) the settings
plot #primary command for drawing 2 D figures.
plot sin(x)
plot ‘datafilename’ using 2:3 with linespoints linetype 1 pointtype 2 title ‘MyFigure’
plot ‘datafilename’ u 2:3 w lp lt 1 pt 2 t ‘MyFigure’ #same meaning as above
splot #drawing 3D figures.

7. save plot to a file Define terminal type and file name
set terminal png
#set terminal to png type
#allow creating png format picture
set output ‘output.png’
#specify the name of the output file
#figure will be saved to the file
#instead of be displayed on the screen

8. plot functions built-in functions define your own function
sin, cos, exp, log, log10, sqrt, norm, abs, etc.
define your own function
+, - , * , / , etc.

9. plot functions
Examples
gnuplot> f(x)=5*x*2+1
gnuplot> plot f(x)

10. plot functions
Examples
gnuplot> plot 3*x+5*sin(x)

11. plot functions
Examples
gnuplot> splot sin(x)+sin(y)

12. add text to plot set title “A Figure” #set the title of the figure
set xlabel “time” #set the x-axis label as time
set label 1 “This is a label1”
#specify the name of a label
set label 1 at graph 0,0
#specify location of label 1, using graph coordinate
#0,0 is bottom left and 1,1 is top right
set label 2 “This is label2” at 3.14, 0
#place the label at a particular x-y coordinate

13. add shape to plot gnuplot> set object 1 rect from 0,0 to 1,4
gnuplot> plot [-5:5] x, -3+sin(x*5)/x lt 3 lw 3

14. plot data file datafile plot script # using 1:2
$ cat plotdata.txt
datafile="./plotdata.txt" set terminal png set output "points.png" plot datafile using 1:2 with points pause -1 "Hit any key to continue”
# using 1:2
# use the 1st and 2nd columns
# with points
# use points to plot data

15. plot data file
result

16. plot data file plot with connected points
datafile="./plotdata.txt" set terminal png set output “linespoints.png" plot datafile using 1:2 with linespoints pause -1 "Hit any key to continue”

17. plot data file
result

18. plot data file plot with all three columns
datafile="./plotdata.txt" set terminal png set output “linespoints.png" splot datafile using 1:2:3 with linespoints pause -1 "Hit any key to continue”

19. plot data file
result

20. multiplot plot in the same figure
plot f1(x), f2(x), ...
Multiplot: plot in multiple subfigures
set multiplot layout <rows>, <cols>
unset multiplot

21. multiplot example gnuplot> set multiplot layout 1,2
multiplot> plot sin(x)
multiplot> plot cos(x)
multiplot> unset multiplot

22. References
Find the demos , tutorials and documents at Visualize your data with gnuplot Display data on webpages

23. Labs
Lab 4
DUE: 11:59pm, Tuesday, April 14, 2015
Lab 5
DUE: 11:59pm, Tuesday, April 28, 2015
(Late submission will not be accepted )