Lesson index || Introduction | MATLAB windows | Getting help | M-files | Summary

M-files

You will need to be familiar with creating, editing and executing M-files. This allows you to

• Store commands for later use. Will you remember in Week 10 the commands you used in Week 2?
• Build up larger and more complicated programs.
• Use the MATLAB editor to debug and then optimize your program.

M-files are just plain text files containing MATLAB commands. An M-file has extension .m for example cubic.m.

An M-file is executed, that is all the commands within the M-file are executed, simply by typing the name of the file (without the .m extension) in the command window.

Downloading M-files

M-files will be provided as examples during your course. You will need to be able to download these from your course web page.

To do this use one of the following methods:

• Left click on the name of the M-file and chose the option to save the file in your account or on your computer.
• If the .m extension is not recognised (for example if MATLAB is not installed on your home computer), then Right-click on the name of the file and choose the "Save Target As ..." (IE) or "Save Link As ..." (Firefox) option.

Save the M-files in an appropriate folder (directory), for example one for each of the courses you are doing.

MATLAB Editor

MATLAB comes with an editor that allows you to easily create and edit M-files. The basic functionality is just like most editors (word processors). However the MATLAB editor also has features useful specifically for writing programs:

• Syntax highlighting
  • Comments (anything beginning with a %) is coloured green. It it very important to use comments to document your M-files, just as MATLAB does.
  • MATLAB keywords are coloured blue. You should not try to change a keyword.
  • Smart indenting can be used so the structure of your programs becomes clearer.
• Debugging
  • Breakpoints can be set on any line of an M-file so you can check the values of your variables and more easily find any mistakes.
  • Profiling can be used to find where your program is spending most of its time, allowing you to produce more efficient code.

Creating a new file

The are several ways of creating a new M-file using the MATLAB editor. These include:

• Click the New Script icon (a page with a + sign) at the top left of the Home tab.
• Use the New (a large yellow plus + sign) icon immediately to the right of the New Script icon. This enables you to create a variety of new objects, in particular scripts and functions (see Lesson 4).
• In the MATLAB command window type edit filename.m.

Editing an existing M-file

The are several ways of opening an existing M-file for editing with the MATLAB editor, including:

• Click on the Open icon, the yellow open folder close to the top left of the HOME tab in the MATLAB window or the EDITOR tab of the MATLAB editor. Then select the appropriate file.
• In the MATLAB command window type edit filename.m. If the file filename.m already exists it will be opened, otherwise you will get a dialogue box asking if you want to create it.
• If you have Current Folder window open, then double clicking a file will open it in the MATLAB editor.

Opening the M-file cubic.m in the MATLAB editor produces a new window similar to the one below:

Do not worry about the meaning of the MATLAB commands for now, but you should try executing the M-file by typing cubic in the MATLAB Command Window.

Matlab demos

MATLAB has a variety of examples and demos, including videos, which explain some of its features.

At this stage the "Getting started with MATLAB" video may be particularly useful.

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