Leaking thoughts out of eSpace
A Quick Start to Octave
Two days ago, I have started working on a new web application that manages a power quality monitoring and analysis system. The system consists of multiple sensors that are spread through multiple locations and periodically send readings to the server which pass the data to an Octave script to process and analyze.
In case you don't know, GNU Octave, as described on its home page, is a high-level language, primarily intended for numerical computations. It provides a convenient command line interface for solving linear and nonlinear problems numerically, and for performing other numerical experiments using a language that is mostly compatible with Matlab.
Today, I'm going to show you how to install Octave on Windows and do some simple tasks.
First, you need to go to GNU Octave Repository and download the latest version of Octave Forge Windows. At the time of this writing, it is version 3.0.1 (octave-3.0.1-setup.exe). Run the downloaded file and follow the installation wizard keeping all default options. Then, use the Windows "Start" menu to open the Octave command window ("All Programs" > "GNU Octave" > "Octave").
So, let's try some commands (always press "Enter" after typing a command):
To exit at any point, just type:
exit
Now, type:
x=1+2
and note that the response is shown in the command window. Then, type:
x=1+2;
and note that the response is not shown.
Type:
x
to show the value of the variable.
Now, type:
who
to show the contents (variables) of the workspace (should now include x).
Type:
clear
to clear the workspace.
Type:
help sin
to get help on the "sin" command.
How about some matrices?
Type the following (press "Enter" after each line):
A = [1, 2, 3] B = [4, 5, 6] 5 * A B'
This will create two matrixes, multiply "A" by 5 and finally get the transpose of "B".
Let's write a script
Type:
pwd
to print the working directory of Octave. For me, the response was:
ans = C:\Program Files\Octave
This is the directory where Octave looks for your scripts (*.m).
Use any text editor, like Microsoft Notepad, to write a simple script and save the file as myscript.m in Octave's working directory. Here is a simple script that generates a plot:
t=[0:.1:100]'; u=-1+0.02*t; y=sin(0.2*t); plot(t,y,t,u) %This is a comment %y (y-axis) is plotted against t (x-axis) %and u (y-axis) is plotted against t (x-axis)
Type myscript (without the file extension .m) in the command window to run the script. Octave will automatically create a separate window to display the plot.
Using Windows Command Prompt
If you want to run Octave scripts without opening a Octave's windows, you just need to add C:\Program Files\Octave\bin to your Path Windows Environment Variable.
Now, you can run a normal Windows Command Prompt and type octave. Type pwd to know the current working directory. For me, the response was:
ans = C:\Documents and Settings\Hatem
Type exit to quit Octave.
Now, to run the script, copy it to the working directory and then type:
octave myscript.m
That's all for today. Later, I may post more details on how I integrated Octave with my Ruby on Rails application.
