notes.m

Matlab numerical methods,examples of mathematical procedures

%NOTES

MATLAB Preliminaries

Matlab File types
  Scripts    are used for storing several executable statements.
  Functions  are used for functions and subroutines.
  MAT-files  are used for storing data.

Editing

  The command window.
  
1. The command window is used for immediate mode entering and display 
   of variables and execution of a MATLAB command. 

2. The command window is used for execution of a functions, subroutines 
   and programs that are stored in an  M-File .

  The edit window.
  
1. The edit window is write and edit functions, subroutines and programs 
   which are to be stored in an  M-File. 

  The graph window

1. The graph window is used to view plotted data.

Diary
  Diary <filename>  directs output to the file
  Diary off         suspends the diary
  Diary on          turns diary on again

Conservation of resources

  Most numerical experiments involve columns of numbers which might extend 
several pages.  It is not necessary to see all of the computations in a project.
Judicious use of diary and files commands such as X(1:5:N) will reduce the 
amount of paperwork.  Before you hand in a project, determine how little is required.


Obtaining Help

  HELP topic  gives help on the topic.
  HELP word  where 'word' is a filename, 
          displays the first comment lines in the M-file 'word.m'.

Housekeeping

  ;      Place at the end of line to suppress the computer echo.
  ,      Used at the end of a line if the computer echo is desired.
  %      This is a comment.

  format short        output displays four decimal places
  format long         output displays fourteen decimal places
  who                 list of variables
  what                list of files
  clear               clear workspace
  clear variables     clear variables
  clear functions     clear functions
  clc                 clear display
  clg                 clear graph

Assignment Statements

  痻 = 2;
  痽 = x^2 -3*x + 2;

Form of a MATLAB Program M-File of executable statements

%  <program-name>
{<specification-statements>}
{<executable-statements>}

Form of a MATLAB Subroutine M-File

function (output-list) = <subroutine-name> (argument-list)
{<specification-statements>}
{<executable-statements>}

Example, store the following subroutine in the M-file;  sroot.m

function  r = sroot(A)
% Newton's method to find  A^(1/2)
p0 = 1;                             % Starting value.
for k=1:50,
  p1 = (p0+A/p0)/2;
  disp(p1);
  if abs(p1-p0)/p1 < eps, break, end;
  p0 = p1;
end

Form of a function (or subroutine) call.