Script m-files                                                                                                              (last updated 9/9/99)

The information in this tutorial is located in Chapter 4 of the MATLAB manual,   The Student Edition of MATLAB, Version 5, The MATH WORKS Inc. Prentice-Hall, 1997.

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This tutorial includes the following sections;

Introduction

Creating and Executing a Script m-file
 
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Introduction

While MATLAB commands are relatively easy to type and execute, it can be tedious when a long list of commands needs to be executed several times, may need to be edited, or stored for later. Saving a MATLAB workspace only saves the values of the variables in memory, not any of the commands. MATLAB gives you a way to handle this by allowing a list of commands to be stored in a simple text file. You can then open the text file and MATLAB will execute the commands as if they were typed at the MATLAB prompt. These text files are called script files or m-files. The term m-file comes from the fact that the script files must have the '.m' extension, filename.m.

The commands in the m-file are executed from the workspace. Any variables in the Command Window are available to the m-file and any variables defined in the m-file will be stored in the Command Window memory upon execution.
 
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Creating and Executing a Script m-file

Creating a script m-file:

• Click on FILE/NEW/M-FILE. This will open the MATLAB Editor/Debugger.  This is not another Command Window. MATLAB commands cannot be executed from here.  Alternately, the NEW FILE icon on the toolbox can be clicked.
• Enter the MATLAB commands you want to execute. Remember the use of the semicolon to suppress output if desired. Also be sure to use comments (the % symbol) spaces, and indents to make your code more readable.
• Save the file by clicking on FILE/SAVE AS in the text editor. Make sure you are in the directory you want. The 3.5"floppy disk is the A drive and the zip disk is the E drive.  Give it a name xxx.m. IT MUST HAVE A '.M' EXTENSION OR IT CAN'T LATER BE EXECUTED.

 

• Return to the MATLAB Command Window.
• Change to the directory you where the m-file is located. For the 3.5" drive this is done by >> cd a:.  For the zip drive this is done by >> cd e:.
• To execute the m-file type xxx at the MATLAB prompt. MATLAB will first look to see if xxx is a variable, then it looks to see if it is a built in MATLAB command, then it looks for a script m-file. For example 'aaa' can be both a variable and there can be an m-file aaa.m. If so, MATLAB will just report the value of the variable.

It is useful to type long arrays in an m-file because it is easy to edit if you make a mistake without retyping the entire array. You then just type the m-file name to put the array into memory.

There is no method available for directly saving a figure or graph. The method is to put all the commands into an m-file which can be saved. This is also very useful when there is a chance that the plot will need edited. When you use the gtext command to locate text on a graph it cannot be removed. If the command is in an m-file it can easily be edited or removed. (See the Plotting Basics Tutorial).

A number of commands for dealing with file management (listing, deleting, etc.) are shown in the table on page 37 of the MATLAB manual.