A very brief introduction to MATLAB

When you start MATLAB, you should see a window appear which contains a number of panes, something like this:

Let's look at the various parts of this window:

Command

Type your commands to MATLAB here -- for example, the commands to run a function, or to set a variable equal to some value. All the output of your functions will appear in this pane, too.

Folder

Use this pane to look for your program files, or to set the folder in which your files will be saved.

Variable

As your program executes, the values of variables will appear here. This is very useful in conjunction with the debugger.

History

All the commands you type are saved here for future reference. You can also use the up-arrow key in the command pane to recall earlier commands.

There are also several windows which may pop up in response to your actions.

The plot window shows any plots which you may create with MATLAB's own plot command.

The editor/debugger window allows you to edit MATLAB programs. You may also use any other text editor to do so, outside of MATLAB, if you wish. However, the editor incorporates the MATLAB debugger, which is a powerful tool.

There are additional windows inside MATLAB, but we probably won't use them very much.

Some basic features of the MATLAB language

• MATLAB is interpreted, not compiled (unless you purchase the compiler and learn how to use it)
• Variables
  • no need to declare in advance -- in fact, can't declare
  • no need to specify type
  • can switch from one type to another
  • assign value with '='
  • if type name all by itself, with no semicolon, value printed to screen (in fact, this is true for any expression which doesn't end in semicolon)
• Workspace
  • save it with save filename
  • restore with load filename
  • record all commands typed with diary filename
  • stop recording with diary off
• Script files
  • place commands into a file mycommands.m (the name doesn't have to end with .m, but it may make the file easy to recognize)
  • type mycommands in the command window, and everything is executed (don't include the ".m" in the name)
• Arithmetic
  • standard operators + - * /
  • exponent operator ^
  • use parantheses to specify order of operations
  • there are no C-like ++ or +=
• Built-in Functions
  • lots and lots and lots of 'em -- see the section on builtin functions on the MATLAB home page or just type help matlab/elfun for the basic math functions
  • all trig functions take arguments in radians (not degrees) and, hooray, pi is pre-defined for you
  • i is pre-defined to mean "square root of negative 1"; square roots of negative numbers yield complex results
  • type help foobar to get help on function "foobar"
• Printing values
  • Method 1: type the variable or expression without semicolon
  • Method 2: use the disp function
  • Method 3: for maximum flexibility, use fprintf (sends output to screen or a file), or sprintf (sends output to a string variable)
  • Example: print to screen: fprintf(1, 'value of a is %7.1f \n', a)
  • note that the format string (like all strings) is defined by single-quote (apostrophe) characters ', rather than by double-quote (quotation marks) characters "
  • Example: to print to a file,
    1. open the file: fid = fopen(filename, 'w')
    2. write to it: fprintf(fid, 'string %s and integer %d\n', str, int)
    3. close the file: fclose(fid)
• Expressions -- for scalar quantities (vectors and matrices have their own set of functions), each of the following expressions will return 1 (true) or 0 (false)
  • equal to: a == b
  • not equal to: a ~= b
    this is not the same as the != comparison in C
  • greater than: a > b
  • less than: a < b
  • greater than or equal to: a >= b
  • less than or equal to: a <= b
• Control Flow
  • If

      if (a == b)          if (a == b)            if (a == b)      
        do this              do this                do this
      end                  else                   elseif (a > b)
                             do that                do that
                           end                    else
                                                    do the other thing
                                                  end
    

  • for

       for i = 1 : 10        for i = 1 : 0.1 : 2
         x = x + i;              x = sin(i);
       end                   end
    

    • note that the limits are inclusive at both ends, unlike C
    • note that if you include the increment, it falls in the middle of the for statement, unlike C
  • while

       while (i < 100)          while (i < 100) 
         do something             do something
       end                        if (result > i)
                                    break
                                  end
                               end
    

    • note that there is no "continue", like in C
    • the break command works in for loops, too

For more information

• The official MATLAB web site includes a great deal of documentation, some of which is in the form of videos.
• There are many university courses which use MATLAB, so you can find many good tutorials with a little searching. For example,
  • Kristian Sandberg's tutorial from the Department of Applied Mathematics at the University of Colorado
  • Edward Neuman's tutorials , from the Department of Mathematics Southern Illinois University

• Wikibooks has an entry on MATLAB programming

Copyright © Michael Richmond. This work is licensed under a Creative Commons License.