A Brief Introduction to Matlab

To start Matlab, at the osf1 prompt type matlab. The matlab prompt looks like this:

 >> 

Matrices and vectors (which is a matrix with a special form) are the underpinnings of everything in Matlab. To enter a matrix, type

A=[2 1 -3;5 7 9;0 8 -4]

Notice the rows are separated by semicolons, the entries in a row are separated by a space. You can also use a comma to separate entries in a row.

By setting A equal to this matrix you can use the letter A to represent this matrix. To recall what is in A, merely type A at the prompt and press enter. You can always change the definition of A by assigning it to something else.

To perform matrix operations on matrices you use the symbols +, -, *, and ^. However, if you want to do scalar operations on each entry in a matrix, you need to use a dot "." in front of these operations. (Functions like sin, cos, log, exp, and tan evaluate the corresponding function of each matrix element.)

To plot the function x squared from 0 to 1 with spacing 0.05, first define a vector x which is evenly spaced from 0 to 1:

x=[0:.05:1]

y=x.*x

y=x.^2

plot(x,y)

• diary filename This stores a file which is a verbatim account of your matlab session. If you are using osf1, you must use this command before you can print your work. The file you create will be saved in your osf1 directory. If you wish to append work to this file at a later date just type in diary and use the same file name.
• diary off The diary file starts at the point where you insert the command diary and ends where you type diary off.
• lpr THIS IS NOT A MATLAB COMMAND. This is the command from the osf1 prompt that you use to print your diary file. Exit the matlab program. At the osf1 prompt, type for example: lpr -Pst220 filename. Note st220 is the printer in ST I room 220. At other locations you will use another printer name after the -P.
• pico, emacs, or vi filename THIS IS NOT A MATLAB COMMAND. Type one of these three at the osf1 prompt to edit a file. Or use the editor of your preference. You will use this on assignments to clean up your work and make it more presentable.
• who Displays variables you have defined in your current session.
• quit or exit either one ends your Matlab session.
• save filename This command will save all variables that you have defined in the current session. This is useful when you have entered large data sets that you will want to work with later.
• load filename this command loads the variables that you saved in a previous session.
• clear Clears all variables from your current session. Only use this command if you want to lose everything.
• % This is used for comments. Matlab ignores any line that begins with a %.
• ; If you put a semicolon at the end of a command, the command will be executed but whatever it creates will not be displayed on screen.
• uparrow Recalls last thing you typed which can then be edited.
• size(A) Gives the size of the matrix A.
• zeros(2,3) Creates the 2 times 3 matrix of zeros.
• format long Displays all numbers with 15 digits instead of the usual 4 digits.