C2110 UNIX and Programming 10th lesson -1C2110
UNIX and Programming
Petr Kulhánek
kulhanek@chemi.muni.cz
National Centre for Biomolecular Research, Faculty of Science,
Masaryk University, Kamenice 5, CZ-62500 Brno
10th Lesson
gnuplot, bash
C2110 UNIX and Programming 10th lesson -2-
Contents
➢ Presentation of Scientific Data
➢ Gnuplot
• overview of the Gnuplot language
• command plot, setting and description of axes
• terminals
• splot command
C2110 UNIX and Programming 10th lesson -3-
Gnuplot
PM3
http://www.gnuplot.info/
(documentation, tutorials, source codes)
C2110 UNIX and Programming 10th lesson -4-
Example
C2110 UNIX and Programming 10th lesson -5-
Example
C2110 UNIX and Programming 10th lesson -6Interactive
mode
Gnuplot is used for rendering of 2D and 3D graphs and enabled work in interactive or
scripting regime.
[kulhanek@wolf ~]$ gnuplot
G N U P L O T
Version 4.4 patchlevel 3
last modified March 2011
System: Linux 3.2.0-31-generic
Copyright (C) 1986-1993, 1998, 2004, 2007-2010
Thomas Williams, Colin Kelley and many others
gnuplot home: http://www.gnuplot.info
faq, bugs, etc: type "help seeking-assistance"
immediate help: type "help"
plot window: hit 'h'
Terminal type set to 'wxt'
gnuplot>
Interactive mode
gnuplot command line
shell Bash command line
C2110 UNIX and Programming 10th lesson -7Non-interactive
mode
1) Indirect launch
We start language interpreter and state the name of the script as an argument.
$ gnuplot my_gnuplot_script
Scripts do not have to have set flag x (executable).
2) Direct launch
We start the script directly (shell automatically starts the interpreter).
$ chmod u+x my_gnuplot_script
$./my_gnuplot_script
Scripts must have flag x (executable) and contain interpreter (part of the script).
#!/usr/bin/gnuplot
plot sin(x)
pause -1
C2110 UNIX and Programming 10th lesson -8Command
- plot
> plot function/file [display_settings] [, function/file ...]
Displays XY graph of a function or data series contained in the file.
Examples:
> plot sin(x)
> plot cos(5.7*x+3.4) with points linecolor rgb "red" \
linewidth 2 title "cos"
> plot "input.txt" using 1:2 with lines
> plot sin(x), cos(x)
lines, points, linespoints, dots color of line
line width key
data file name
the first column contains the x values
the second column contains the y values
displays the functions sin and cos in one graph
C2110 UNIX and Programming 10th lesson -9Exercise
I
1. Plot the graph of y = x2 function
2. Plot the graph from previous task with blue color
3. Display dependence of temperature on time contained in the file:
/home/kulhanek/Documents/C2110/Lesson10/temp.txt
Time is in the first column, temperature is in the second column.
4. Display function sin(x) using red line and cos(x) using orange line and points into one
graph.
Perform tasks in interactive mode
C2110 UNIX and Programming 10th lesson -10Other
commands
> set title "description" # graph header
> set xrange[min_value:max_value] # sets range of x axis
> set xlabel "description" # sets description of x axis
> set yrange[min_value:max_value] # sets range of y axis
> set ylabel "describtion" # sets description of y axis
> set nokey # does not display key for all data series
> pause -1 # waits for pressing of a key
C2110 UNIX and Programming 10th lesson -11Exercise
II
1. Write a script, which will plot function y = x2 in the range of 0-10 for the x-value. Launch
the script indirectly using gnuplot interpreter.
2. Write a script that will display dependence of temperature on time contained in the file
/home/kulhanek/Documents/C2110/Lesson10/temp.txt
Put labels on axis including units, time is in picoseconds, temperature is in kelvin.
C2110 UNIX and Programming 10th lesson -12-
Terminals
Terminal determines where the graph is going to be plotted.
> set term x11 # output is rendered into a window
> set term wxt # output is rendered into a window (better properties)
> set term png size 800,600
# output is rendered as a png image
> set output "output.png" # output is saved to the "output.png" file
> test # prints page demonstrating properties of given
terminal (not all terminals have the same output
options)
C2110 UNIX and Programming 10th lesson -13Output
from different terminals
wxt
postcript/eps
Support of dashed lines
C2110 UNIX and Programming 10th lesson -14Exercise
III
1. What are properties provided by terminals x11 and wxt. Work in interactive mode and
use command test
2. Write a script, which will plot function y = 5x3 + 6x2 - 7 in the range from -10 to 5 for xaxis.
Run the script directly specifying the interpreter in the header of the script.
3. Modify the previous script so that the graph is rendered as a png image into a file. Size
of the image will be 640x480. Display the image file using command display.
4. Display the result of the command test for the terminal png and postscript.
5. What are type of terminal supported by gnuplot (set terminal command without an
argument)?
C2110 UNIX and Programming 10th lesson -15splot
command
> splot function/file [display_settings] [, function/file ...]
Displays XYZ graph of a function or data series contained in a file.
splot command can be used to display functions of two variables.
View is set by the command set view a, b, where a and b are directional angles. Top view
can be set by set view map
Surface can be colored based on the functional value by using display option pm3d, e.q.:
> splot x*x+y*y with pm3d
While visualizing functions, density of the sampling for x-axis and y-axis can be set by
command set isosamples a, b, where a and b indicate the number of samples in the given
direction.
C2110 UNIX and Programming 10th lesson -16Exercise
IV
1. Display function x2 + y2
2. Set view from the top (command set view)
3. Disable view from the top (unset view)
4. Increase the density of points for the visualization of the function (set isosamples).
Use values 10,20; 20,10 and 20,20
5. Use pm3d display option
6. Set view from the top (set view)
Work in the interactive mode
C2110 UNIX and Programming 10th lesson -17-
Bash
➢ Redirection of the input from a script
C2110 UNIX and Programming 10th lesson -18Redirection
of input from script
Redirection of standard input of program my_command from the script file.
.......
./my_command << EOF
first line of text
second line of text
third line of text
EOF
......
sign indicates the end of input
(user selectable)
end of input, sign must not be
surrounded by spaces
text, that is loaded as input
This type of redirection is particularly advantageous in scripts but works also in the command line. The
advantage is the expansion of variables in read text.
C2110 UNIX and Programming 10th lesson -19-
Examples
#!/bin/bash
gnuplot << EOF
plot sin(x)
EOF
#!/bin/bash
for((I=1;$I<=10;I++)); do
NAME=`printf "%02d.txt" $I`
cat << EOF > $NAME
This is a file number: $I
EOF
done
Highlighted text is sent to the standard
input of cat command, variables are
expanded before sending the output, then
cat saves the output to the file $NAME.
This construction allows to automatically create
scripts for gnuplot.
Result of commands in graves `` is
assigned to variable NAME.
C2110 UNIX and Programming 10th lesson -20Exercise
V
1. Create a script that will create 360 images with size 800x600 of function sin(x + offset)
for x in the interval from 0 to 2π, where the constant for offset will vary gradually from
1 to 360˚.
2. Create a script that will create ten files. The file name will be in format XX.txt, where XX
is the file number. If the file number is less than ten, use 0 as the first digit. Each file
will contain the following text (where X is file number):
Automatically generated text file
File number is: X