MATLAB is a technical computing environment for high-performance numeric computation and visualization. MATLAB integrates numerical analysis, matrix computation, signal processing and graphics in an easy-to-use environment where problems and solutions are expressed just as they are written mathematically - without traditional programming.
MATLAB is an interactive system whose basic data element is a matrix that does not require dimensioning. This allows you to solve many numerical problems in a fraction of the time it would take to write a program in a language such as Fortran, Basic or C.
MATLAB also features a family of application-specific solutions called toolboxes. Toolboxes are collections of MATLAB functions (M-files) that extend the MATLAB environment in order to solve particular classes of problems.
In the College of Engineering, the following toolboxes are available:
To find out what toolboxes are available on a UNIX system, type the command ver on the matlab prompt.
MATLAB is available on all platforms using the same license. The current version is 7.6
As you become familiar with MATLAB, you will probably want to create your own library of MATLAB-related files. It is recommended that you create a new directory called MATLAB in your home directory:
% cd % mkdir matlab % cd matlab
MATLAB's search path is set up to look for files in this subdirectory. Storing your MATLAB related files in the Matlab directory gives you access to them no matter where you are in your file system when you invoke MATLAB.
To invoke MATLAB, enter the command matlab at the operating system prompt. The MATLAB banner appears with the MATLAB prompt ">>". At this point, the MATLAB interpreter is awaiting instructions from you. Enter a small matrix, place brackets around the data and separate the rows with semicolons:
A = [ 1 2 3; 4 5 6; 7 8 9]
When you press Return, MATLAB responds with:
A = 1 2 3 4 5 6 7 8 10
To invert this matrix, enter
B = inv(A)
To edit mistyped commands or recall previous command lines, you can use the arrow keys. For example, if you misspell sqrt in the command
Instead of retyping the entire line, press the key. The last command you entered dis- plays. You can press key to move the cursor left, backspace to delete r and the r key to insert the r in the right place.
The commands you enter during a MATLAB session are stored in a moderately sized input buffer. You can "smart recall" to recall a previous command whose first few characters you specify.
As you become proficient with MATLAB, you will do an increasing amount of work with M-files. M-files contain a series of MATLAB statements and these files are created and edited with text editors such as vi, Emacs, etc. You can use a separate window for running the editor. M-file is a record of how a problem was solved and automates command entry as well as allows user defined function that can be executed from the command line in the future.
Use the exclamation point character ! within MATLAB to indicate the input line is a command to the operating system. This is useful for running any UNIX utility or other program, without exiting from MATLAB. When the external process completes, control returns to MATLAB.
A help facility provides on-line information for most MATLAB topics. The command help with no arguments displays a list of directories that contain MATLAB related files. Each line displayed lists the name of a directory followed by a description of the directory contents. Some of the directories are associated with the base MATLAB itself; they contain information about the functions that are built in the core MATLAB processor, or included M-files with every copy of MATLAB. Other directories are for toolboxes; these contain collections of additional MATLAB functions covering more specialized application areas. For a list of functions covered by a particular directory, type help followed by the directory name (help matfun). Often the names listed are functions, so help followed by one of these names provides detailed information about that feature (help eig).
A more general information search is provided by lookfor. This command is like using the index in a book and is similar to the UNIX apropos command (lookfor inverse). Three other commands, who, what, and which, give information about variables, file, and directories. Type help who, help what, and help which to find out details.
For additional help, you may try Matlab's site on the Internet at http://www.mathworks.com.
Typing demo at the MATLAB prompt demonstrates some of MATLAB's capabilities and uses a menu called Expo.
The diary command creates a diary of your MATLAB session in a disk file. (Graphics are not saved) The resulting ASCII file is suitable for inclusion into reports and other documents using any word processor.
MATLAB's various plotting functions create windows that contain graphics. The print filename command can be executed to create a postscript file of the active figure which is placed in your root directory. From a unix prompt you can then send the postscript file to the printer using the "lp" command.
Before attempting to run a matlab program in background, remove any graphic commands, such as plot, etc from your file, my_file.m. Then use the following to run your m-file in background on one of the servers:
nohup matlab < my_file > outfile
The 'nohup' will enable the program to keep running after you logoff the server. The '&' will tell the server to run the command in background. Outfile is where your output will be stored.
If you are running in background, you will probably also want to save the output from your variables also.
save foo [var1 [var2 [...]]]
This will create a file called foo.mat. If you do not specify any variables, then Matlab will save your entire workspace (this can be quite large). To retrieve the data in foo, use 'load foo' in the Matlab window.
( type as seen at the MATLAB prompt >>)
sqrt(-1) x = [-1 0 2] x = x' y = x - 1 inprod = x'*y outprod = x*y' who A = [1 2 3; 4 5 6; 7 8 0] B = A' B(1,1) B(:,1) B(1:2,:) x(3) C = A + B b = A*x x = inv(A)*b z = pi*x who w = x*y w = x.*y u = x^2 u = x.^2
z = cos(pi/3) z = [-1:0.05:1]' zz = cos(2*pi*z) plot(z,zz) plot(z,zz,z,zz,'ro') zz = exp(-1.5*z).*cos(2*pi*z) plot(z,zz,z,zz,'ro') title(`Figure 1'); xlabel(`Time'); ylabel(`Amplitude'); grid
(create a file called bumps.m in your root directory. It should include:) function y = bumps(x) y = 1./((x-.3).^2+.01) + 1./((x-.9).^2+.04) - 6 (then at the prompt >>) x = -1:0.01:2; plot(x,bumps(x)) fplot(`bumps',[-1 2],0.01)
x=-8:0.5:8; y = x; [X,Y]=meshgrid(x,y) plot(X,Y,'.') R = sqrt(X.^2 + Y.^2) +eps Z = sin(R)./R contour(x,y,Z,10) mesh(x,y,Z) meshc(x,y,Z)
The 20 categories listed below provide command and function reference tables for their associated topic. To find "general" commands and functions for MATLAB, at the MATLAB prompt ">>", enter:
To find MATLAB operators and special characters, at the MATLAB prompt ">>", enter:
Category Description -------- ------------------------------------------------ general General purpose commands ops Operators and special characters lang Language constructs and debugging elmat Elementary matricies and matrix manipulation specmat Specialized matricies elfun Elementary math functions specfun Specialized math functions matfun Matrix functions - numerical linear algebra datafun Data analysis and Fourier transform functions polyfun Polynomial and interpolation functions funfun Function functions - nonlinear numerical methods sparfun Sparse matrix functions plotxy Two dimensional graphics plotxyz Three dimensional functions graphics General purpose graphics functions color Color control and lighting model functions sounds Sound processing functions strfun Character string functions iofun Low-level file I/O functions demos Demonstrations and samples