The MATLAB Environment (Getting Started)

Getting Started with MATLAB

The MATLAB environment includes both the set of variables built up during a MATLAB session and the set of disk files containing programs and data that persist between sessions.

The Workspace

The workspace is the area of memory accessible from the MATLAB command line. Two commands, who and whos, show the current contents of the workspace. The who command gives a short list, while whos also gives size and storage information.

Here is the output produced by whos on a workspace containing results from some of the examples in this book. It shows several different MATLAB data structures. As an exercise, you might see if you can match each of the variables with the code segment in this book that generates it.

whos

  Name      Size         Bytes  Class

  A         4x4            128  double array
  D         5x3            120  double array
  M        10x1           3816  cell array
  S         1x3            442  struct array
  h         1x11            22  char array
  n         1x1              8  double array
  s         1x5             10  char array
  v         2x5             20  char array

Grand total is 471 elements using 4566 bytes.

To delete all the existing variables from the workspace, enter

clear

save Commands

The save commands preserve the contents of the workspace in a MAT-file that can be read with the load command in a later MATLAB session. For example

save August17th

saves the entire workspace contents in the file August17th.mat. If desired, you can save only certain variables by specifying the variable names after the filename.

Ordinarily, the variables are saved in a binary format that can be read quickly (and accurately) by MATLAB. If you want to access these files outside of MATLAB, you may want to specify an alternative format.

`-ascii`	Use 8-digit text format.
`-ascii -double`	Use 16-digit text format.
`-ascii -double -tabs`	Delimit array elements with tabs.
`-v4`	Create a file for MATLAB version 4.
`-append`	Append data to an existing MAT-file.

When you save workspace contents in text format, you should save only one variable at a time. If you save more than one variable, MATLAB will create the text file, but you will be unable to load it easily back into MATLAB.

The Search Path

MATLAB uses a search path, an ordered list of directories, to determine how to execute the functions you call. When you call a standard function, MATLAB executes the first M-file function on the path that has the specified name. You can override this behavior using special private directories and subfunctions.

The command

path

shows the search path on any platform. On PCs and Macs, choose Set Path from the File menu to view or modify the path.

Disk File Manipulation

The commands dir, type, delete, and cd implement a set of generic operating system commands for manipulating files. This table indicates how these commands map to other operating systems.


MATLAB	MS-DOS	UNIX	VAX/VMS
`dir`	`dir`	`ls`	`dir`
`type`	`type`	`cat`	`type`
`delete`	`del or erase`	`rm`	`delete`
`cd`	`chdir`	`cd`	`set default`

For most of these commands, you can use pathnames, wildcards, and drive designators in the usual way.

The diary Command

The diary command creates a diary of your MATLAB session in a disk file. You can view and edit the resulting text file using any word processor. To create a file called diary that contains all the commands you enter, as well as MATLAB's printed output (but not the graphics output), enter

diary

To save the MATLAB session in a file with a particular name, use

diary filename

To stop recording the session, use

diary off

Running External Programs

The exclamation point character ! is a shell escape and indicates that the rest of the input line is a command to the operating system (or to the Finder on the Macintosh). This is quite useful for invoking utilities or running other programs without quitting MATLAB. On VMS, for example,

!edt magik.m

invokes an editor called edt for a file named magik.m. When you quit the external program, the operating system returns control to MATLAB.

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