TABLE OF CONTENTS Although you can do many useful computations working entirely at the MATLAB command line, sooner or later you will need to write M-files. These are the equivalents of programs, functions, subroutines and procedures in other programming languages. Collecting together a sequence of commands into an M-file opens up many possibilities, including
experimenting with an algorithm by editing a file, rather than retyping a long list of commands.
making a permanent record of a numerical experiment,
building up utilities that can be reused at a later date,
exchanging M-files with colleagues.
Many useful M-files that have been written by enthusiasts can be obtained over the internet; see Appendix C.
An M-file is a text file that has a .m filename extension and contains MATLAB commands. There are two types:
Script M-files (or command files) have no input or output arguments and operate on variables in the workspace.
Function M-files contain a function definition line and can accept input arguments and return output arguments, and their internal variables are local to the function (unless declared global).
A script enables you to store a sequence of commands that are to be used repeatedly or will be needed at some future time. A simple example of a script M-file, marks.m, was given in Section 2.1. As another example we describe a script for playing "eigenvalue roulette" [15], which is based on counting how many eigenvalues of a random real matrix are real. If the...
