Skip to content Skip to navigation Skip to collection information
(What does "Endorsed by" mean?)
Inside Collection: A First Course in Electrical and Computer Engineering
You should write a MATLAB program whenever you anticipate exe- cuting some sequence of statements several times or again in a later session. On an IBM PC, you may use any text editor to write a program, as long as the file can be saved in ASCII format without the control codes used by most word processors. Applicable text editors include Edix, Wordstar, XTree Pro, and Turbo Pascal's editor.
Editing Files. If you have enough memory, you can run your editor without leaving MATLAB by using the exclamation point (!), like this:
≫ !EDIXThe exclamation point may be used to execute any DOS command or program
from MATLAB. When the command or program finishes, your MATLAB
variables are just as you left them. Use your editor to write program lines
just as you would type them in MATLAB's command mode. Then save the
file with extension .m in the directory where you will run MATLAB. Such
MATLAB programs are called m-files. You may run your m-file by typing the
file name (without the .m extension) at the MATLAB command prompt
Script Files. There are two kinds of m-files, called script files and
functions. Running a script file is exactly like typing the commands it contains
at the plotsin.m as listed next:
t = -6:.2:6;
y = sin(t);
plot(t,y)
title('SINE')
pause
grid
xlabel('t')
ylabel('sin(t)')
When the pause is executed, you will need to press a key to go on. If you type
whos after running plotsin, you will see that the variables t and y remain
in memory. Comments are important to a script file. They are marked with
the symbol %. Anything following this symbol on a line is assumed to be a
comment and is ignored by the MATLAB program interpreter.
Functions. Functions differ from script files in that they have designated input and output variables. Any other variables used within a function are local variables, which do not remain after the function terminates and which have no effect on variables outside the function. Many of the functions supplied with MATLAB are actually m-files. A good example is triu.m:
≫ type triuThe word function at the beginning of the file makes it a function rather than
a script file. The function name in this line must match the file name. The
input variables of triu are x and k, meaning that the first input argument
will be referred to as x and the second as k within the function. Likewise,
the function line designates y as the output. There is nothing special about
the variable names x,k, and y when the function is used. It is only that
whatever inputs and output you use will be referred to as x,k, and y inside
the function. The variables m,n,j, and i are created temporarily when triu
runs and disappear when it terminates. They are local variables and have no
effect on variables with the same names outside the function. In contrast, a
script file has no local variables and does no substitution of input and output
variable names.
As an exercise, enter and save the function perp.m:
function y=perp(x)
% PERP(x) is a complex number perpendicular to x.
j = sqrt(-1);
y = j*real(x)-imag(x);
Evaluate perp on various complex numbers. Replace the last line by y = x*j;. Do you get the same result? Why?
Printing Files and Graphics. To display an m-file on the screen,
use the instruction ≫ type filename. To make a copy at a printer, use
the DOS command ≫ !print filename.m. Graphics hardcopy is available
through the commands meta and gpp. See the MATLAB manual for more
information.
More about this module: Metadata | Downloads | Version History
This work is licensed by Louis Scharf under a Creative Commons Attribution License (CC-BY 3.0), and is an Open Educational Resource.
Last edited by Daniel Williamson on Sep 16, 2009 12:15 pm -0500.
"Reviewer's Comments: 'I recommend this book as a "required primary textbook." This text attempts to lower the barriers for students that take courses such as Principles of Electrical Engineering, […]"