Start MATLAB on your machine. You get a prompt like
this:

`>>`

Here are some things you can do.

>> diary on % Causes Matlab to save a record of the session in a % file named diary. Later you can edit this file, % print it out, turn it in as homework, or whatever. % For more information about diary, type ``help diary'' >> a = [1 2 ; 3 4] a = 1 2 3 4 >> x = ones(2,1) x = 1 1 >> b = a*x b = 3 7 >> y = a\b % Solves system Ay=b for y. y = 1.0000 1.0000

>> c = a' % transpose c = 1 3 2 4 >> H = a'*a H = 10 14 14 20 >> chol(H) % upper triangular Cholesky factor ans = % The default variable name is ans. 3.1623 4.4272 0 0.6325 >> m = ans m = 3.1623 4.4272 0 0.6325 >> A = a^2; % exponentiation. Semicolon suppresses printing of result. >> A % To have a variable printed out, just type its name. A = % Matlab is case sensitive: A and a are different. 7 10 15 22 >> A(1,1) = A(1,1) + 13 A = 20 10 15 22 >> [L U] = lu(A) % LU decomposition (with pivoting if necessary) L = 1.0000 0 0.7500 1.0000 U = 20.0000 10.0000 0 14.5000 >> AI = inv(A) AI = 0.0759 -0.0345 -0.0517 0.0690 >> p = A*AI p = 1.0000 0 0 1.0000 >> format long % some alternative formats >> p p = 1.00000000000000 0 0 1.00000000000000 >> format short e >> p p = 1.0000e+00 0 0 1.0000e+00 >> format % The default format is called `short'. >> p p = 1.0000 0 0 1.0000 >> a = hilb(3) % 3 by 3 Hilbert matrix a = 1.0000 0.5000 0.3333 0.5000 0.3333 0.2500 0.3333 0.2500 0.2000 >> b = 1:3 b = 1 2 3 >> b=b' b = 1 2 3 >> x=a\b x = 27.0000 -192.0000 210.0000 >> r=b-a*x

r = 1.0e-14 * % scale factor for the array 0 -0.7105 0 >> n = norm(r) n = 7.1054e-15 >> cond(a) ans = 524.0568 >> a = zeros(4,4) a = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 >> for i=1:3 a(i+1,i)=1; % a simple loop a(i,i)=2; % The whole thing could have gone on one line. a(i,i+1)=3; end >> a(4,4)=2; >> a a = 2 3 0 0 1 2 3 0 0 1 2 3 0 0 1 2 >> quit % Quit MATLAB % Some other useful commands are: >> intro >> demo >> help >> help help >> help elmat >> help eig >> help plot >> help sparse >> help [name your favorite topic] % Other commands are less useful: >> why % Chances are, you are running a recent version of MATLAB with % a GUI interface. In this case you can do lots of things using % the pulldown menus and push buttons. There is also a built-in % editor.

2004-01-15