What has happened is that MATLAB interprets ``x = 1 + 2 +3'' as a complete command, and returns x=6. In the next line ``+4+5;'', MATLAB thinks that you just want to add 4 and 5 together, with the trailing semicolon (;) meaning that you are not interested in the answer.

   While this behavior causes no problems at the command line, within a MATLAB program it can cause incorrect results with absolutely no indication of any problems.

      xx = [ 1   23  3;
             2  720  4;
             3   11  1;
             4   12  2 ];   

      xx = [ 1   23  3;
             2  720  4;
             3   11  1.5;
             4   11  1.5 ];   

    1.0000   23.0000    3.0000
    2.0000  720.0000    4.0000
    3.0000   11.0000    1.5000
    4.0000   11.0000    1.5000  

   However, MATLAB has borrowed (and slightly improved) a function from C/Java for better displays of matrices or tables. If you enter in a program (or in the MATLAB command window):

   fprintf('  %d   %3d   %4.1f\n', 3, 11, 1.5)  

 
      3   11   1.5  

 
      3.0000   11.0000   1.500  

   In the `format string' ' %d %3d %4.1f\n' in the fprintf() command,

    %d     stands for `display as integer'
    %3d    stands for `display as integer, using AT LEAST 3 spaces, right justified'
    %4.1f  stands for `display as number with possible fractional part,
             using AT LEAST 4 spaces, with 1 SPACE beyond the decimal point'
    \n     stands for end-of-line (or new line), which you must say explicitly
 

   If fprintf() has a matrix argument after the format string, each COLUMN of the matrix is matched to the format items in the format string. In this case, you will usually want to use the TRANSPOSE of a matrix as the argument in the data. For example, for the 4x3 matrix xx defined above

   fprintf('  %d   %3d   %4.1f\n', xx')  

      1   23    3
      2  720    4
      3   11    1.5
      4   11    1.5     

   A FINAL COMMENT: In MATLAB, you MUST ENCLOSE the format string with single quotes (' ') and NOT double quotes (" "). The latter will give a format error. In contrast, in C or JAVA, you MUST USE double quotes to enclose the format string, and single quotes will give a format error. This difference takes a bit of getting used to if you are more used to C or MATLAB and switch to the other.

   MATLAB also has a feature for defining and using a subroutine or function within the same MATLAB program file. For example, if you say

near the top of your MATLAB program file, then f(x,y) will evaluate as x^2+y^2 in the rest of your program, and in particular f(2,3)=13.

   This feature works by MATLAB parsing the single input string in the inline() function for strings of characters that are valid MATLAB variable names, which are an alphabetical character (a-z,A-Z) followed by alphanumeric characters (a-z,A-Z,0-9) up to the next non-alphanumeric character. Thus

defines exactly the same function. Enter help inline or doc inline at the MATLAB command line for more information.

     Start | All Programs | Accessories | Command Prompt

If the window opens with marginally-legible light-grey text on a black background, enter

     color F0

(that is, ``color F-zero'') in the command-prompt window. You will now get legible black lettering on a parchment-white background in the Command-Prompt Window, exactly as in a Notepad window.

   Navigate to your directory of choice by using cd (``change directory'') commands in the command-prompt window. Then enter matlab at the command line. The program MATLAB will now appear with that directory as the Current Directory.

   You can call MATLAB from the command line to execute a particular program file and write the (Command-Window) output to a textfile by entering

     matlab   -r myfile.m   -logfile myoutputfile.txt

MATLAB will run the program file myfile.m as soon as it loads and write the output to myoutputfile.txt. The program MATLAB will remain open, but can be closed in the usual way unless you want to use it further.
   The Windows batch file cmatlab.bat on the Math408 Web site automates this process. That is, enter cmatlab myfile to (i) load MATLAB, (ii) run myfile.m, and (iii) write Command-Window output to myfile.txt. The batch file cmatlab.bat includes options to make MATLAB run faster by not loading the full MATLAB GUI window, but does leave open a more primitive version of MATLAB, which you might still want to close.