Tutorial:
Octave
http://octave.org is a free software tool for numerical
analysis and visualization. The function and command syntax is very similar
to MATLAB. Note that there is no SIMULINK-like tool in
Octave, but there are many simulation functions (as in Control System Toolbox
in MATLAB). Extra packages for Octave are documented on https://octave.sourceforge.io/,
for example the control package which contains
functions for modeling, analysis, simulation, and control of dynamic systems
(similar to the Control System Toolbox in MATLAB). Information about
installation and loading of packages is given at the bottom of this tutorial. Windows in the Octave IDE (integrated development environment)
Three windows are available by default (they can
be opened either via the Window menu or from tabs at the bottom of the Octave
main window). ·
Command Window ·
Editor ·
Documentation The command window
We try the following simple commands from the
command line (the command are executed by pressing Enter):
Octave functions are vectorized, i.e. functions
can be called with vectorial arguments and the function is applied to each of
the elements of the vector:
Workspace
All variables generated during the session
are stored in the workspace. The workspace is cleared when you quit Octave.
We try a few commands:
Help!
Command line help: help command. Example:
Documentation: ·
Help menu ·
Web: http://octave.org
-> docs ·
Google search Scripts
An Octave script is a user-written text file
of name *.m containing any Octave
expressions. When you run the script, all the expressions are execued
automatically as if they were written on the command line individually. You can edit a script using the inbuilt
editor available in the Editor window (via the Eitor tab), or using any other
text editor, e.g. Notepad. You can run a script in several ways: ·
F5 button ·
Via the Run menu in the Editor window ·
By typing the script name (without the file
extension m) on the command line You should use
scripts even for small tasks! Avoid using script
names that are existing variables, commands or function names! Example:
Just after tryiing to run a script, you may
be asked by Octave to change the current
directory of Octave to where the script is stored. Normally, you
can accept the suggested change. Matrix (or array) operations
Creating matrices. Getting matrix information:
Special matrices:
Matrix calculations:
Matrices can be used in matrix calculations.
A few examples:
Elementwise calculations:
The dot operator
implements elementwise calculations, as .*
and ./ and .^. Example:
Plotting
Examples: 1. Single diagram with multiple
curves: 2. Multiple plots as subplots: Extra function packages
Extra function packages for Octave are
available at https://octave.sourceforge.io/ Information about listing of already
installed packages and installation of new packages are given on the above
web page. As an example, open the home page of the Control package. The list of functions is
opened via the function reference link on the web
page. At the start of a session, the package must
be loaded into Octave with the command load package_name
at the Octave command line. Example scripts with the Control package
The following scripts
assumes that the Control package has been loaded into
Octave. 1. Simulation and calculation and plotting of poles and zeros of transfer
functions: 2. Frequency response: 24 Oct 2018. Finn Haugen (finn.haugen@usn.no) |