%-------------------------------------------------------------------------------
% CS100J, Spring 2001
% Thurs 4/19
% Lecture 24
%-------------------------------------------------------------------------------
% This file will run in MATLAB!
%-------------------------------------------------------------------------------
% Notation:
% + The percent symbol (%) means that MATLAB treats everything that follows as a
% comment which is ignored by MATLAB.
% + Anything surrounded by dollar signs ($something$) means a portion of MATLAB
% or a MATLAB command that you would enter.
% + menus: "->" means selecting a submenu
% example) File->Set Path means "click on File menu then click on Set Path
% submenu"
% + you might wish to uncomment one of the following two lines:
% more on % turns pager on
% more off % turns pager off
%-------------------------------------------------------------------------------
% Programming in MATLAB (Matrix Laboratory)
% + two places to put MATLAB statements:
% - Command Window (workspace)
% - Edit Window (M-File)
%
% Command Window
% + MATLAB's "main" window
% - enter commands at prompt (>>)
% - type a command and then press Return or Enter
% - this is the "brain"
% + carves up memory for programs
% + acts upon commands and lines of code
% + The "brain" is called the MATLAB workspace or base workspace:
% - processes and evaluates commands
% - remembers variables and commands you have entered
% + key strokes for short cuts:
% - recalling commands: up and own arrow keys
% - editing editing commands: left and right arrow keys, Backspace, Del,
% Home, something called "Emacs"
% - interrupting evaluation: Control-C (hold Ctr key and press c)
%-------------------------------------------------------------------------------
% + "Help" commands
% helpinfo % very general help (help on ways to get help)
% help % get help on a command
% helpwin % window contain help
% helpdesk % more extensive HTML help browser
% lookfor % search for keword
% which % look for commands and files
% demo % MATLAB demonstration
% + Command options
% - enter $help$ <cmd> where <cmd> is the name of a command
% - many commands have options that modify the command's behavior
% - example)
more
more on
more off
echo on
echo off
% - most commands here have options not shown!
pause
clc
%-------------------------------------------------------------------------------
% + Handy commands:
% more on % turn on pager (spacebar)
% clc % clear screen
% clear % clear variable assignments
% who % check current variables (see also File-> Show Workspace menu)
% whos % long form of $who$
% format % set output preferences (see also File-> Preferences menu)
% computer % type of computer
% version % version of MATLAB currently used
% ver % more explicit than $version$
% diary % save results of current session
%-------------------------------------------------------------------------------
% Edit Window
% + want to enter multiple commands
% + becomes tedious doing this in Command Window
% + store statements in separate file called M-File (also called script file)
% (script because MATLAB will read and process each statement in succession)
% + create file, store statements, run "program" in Command Window
% - create ASCII (also called text) files:
% File->New->M-File or use text editor
% - name of file is the program name
% example) blah.m has the name $blah$
% - set path
% + to load M-File into workspace, MATLAB need to know locaiton of file
% + MATLAB has search path: a list of directories or folders where
% MATLAB looks to find commands which are stored in M-Files
% + You may see path by entering $path$
% + to add directory or folder to path, use File->Set Path, $editpath$,
% or $addpath$
%-------------------------------------------------------------------------------
% examples:
% path % what are currently known paths
% editpath % open pathbrowser to edit path
% addpath % command line method
% - miscellaneous directory commands:
% pwd, cd % show current working directory for Command Window
% place where MATLAB will store files by default
% what % M-Files in current directory
% type % show contents of M-File in Command Window
% exist % check if M-file exists
% dir, ls % show all files in current directory
%-------------------------------------------------------------------------------
% + saving work
% - diary file:
% % diary % open text file named diary in current directory
% % save subsequent work in Command Window to diary file
% - File->Print
% + variables and files
% - saving:
% + menu: File->Save Workspace As
% + CW: $save$ saves variables to file matlab.mat in MATLAB binary format
% (unreadable to human, only MATLAB understands it)
% + CW: $save$ <file> saves variables to file called <file>
% + CW: $save$ <var1> <var2> ... saves jsut those variables
% Many more options! see also "functional form" in $help save$
% - loading:
% + menu: File->Load Workspace
% + CW: $load$ (see $save$: many options!)
% - deleting:
% + CW: $delete$
%-------------------------------------------------------------------------------
Language elements:
pause
clc
echo on
% Examples of tokens and expressions
%============%
% Separators %
%============%
% blank spaces
% you may supply as many as you wish between language elements
% do not separate within a command: example) he lp
% example that works:
help help % lots of spaces inserted and no change in behavior
pause % special
clc
%==========%
% Comments %
%==========%
% MATLAB ignores anything following a % sign on the SAME line
pause
%=========%
% Numbers %
%=========%
1 % integer (whole number)
1.1 % floating point number (decimal)
1e2 % floating point number (scientific notation)
27i % imaginary
27j % imaginary
pause
%===========%
% Operators %
%===========%
1+2 % add
1-2 % subtract
1*2 % times
1/2 % divide
1^2 % power
pause
% Operator precedence
% Operator associativity
% ----------------------
mostly the same rules
% More information
% ----------------
help arith
help ops
help slash
help relop
%===========%
% Variables %
%===========%
% token that stores another quantity in memory
% acts like a placeholder for a value
% example) $x = 1$ stores the value of $1$ in variable $x$
% rules:
% + case-sensitive (for example, $A$ does not mean $a$!)
% + only 31 characters (can go more, but extras are ignored)
% + start with a letter
% + characters may include digits (0-9) and the underscore (_)
% examples) x, x1, x_1
% assignments
% -----------
% To store a value in a variable, use an assignment statement
% Syntax: $var = expression$
% MATLAB evaluates the expression, carves out a portion of memory, and
% stores the value of the expression in $var$.
% Other features:
% + You may not use unassigned varibles.
% + The equals sign (=) means ASSIGN in MATLAB, not equals!
% + When talking of algorithms, write an assignment with an arrow.
% example) "x <- 1" in English means $x = 1$ in MATLAB.
%
% More examples of assignments:
% x % $x$ is not assigned a value, so MATLAB cannot evaluate
x = 1 % assign $1$ to $x$
x = 2 % you change a variable's assignment
x % once assigned, you may check a variable's assignment
% recalling variable values
% -------------------------
% You may use assigned variables in expressions.
% Until you clear variables, restart MATLAB, or assign new values,
% variable values remain in memory as long as your current MATLAB session
% keeps running.
% example)
x = 1 % assign 1 to $x$
y = 2 % assign 2 to $y$
z = x+y % evaluate $x + y$ and store the result (3) in $z$
x = 4 % assign $x$ to a new value
z % $z$ is still 3 and NOT 4+2 because $z$
% was already assigned BEFORE $x$ changed to 4
% predefined variables
% --------------------
% MATLAB comes with useful value already built-in for your convenience!
ans % default name for evaluated expressions without assignments
pi % numerical pi
eps % smallest number that can be added to 1 to make number bigger
% than 1
inf % positive infinity
NaN % not-a-number (ex: 0/0)
nan % not-a-number (ex: 0/0)
i % imaginary number (square root of -1)
j % imaginary number (square root of -1)
realmin % smallest usable positive number in MATLAB
realmax % smallest usable negative number in MATLAB
% You may actually change these values (usually with $eps$)
eps=0.1 % Assign $eps$ to a new value (0.1)
% To restore a predefined variable's value, see $clear$ below.
% clearing variables
% ------------------
% Sometimes you might wish to clear an assigned variable's value.
% You may restart MATLAB with $clear$
clear % you may clear all variables of assignments
% To clear just one variable, enter $clear var$:
x = 1 % assign 1 to $x$
clear x % unassign $x$
% x % test value of $x$
% Use $clear$ to restore predefined variable values.
% You may also enter $clear var$ to clear a specific variable:
eps =0.1 % change value of $eps$
clear eps % restore $eps$
eps % see default value (2.2204e-16)
%=============%
% Punctuation %
%=============%
% comments: %
% suppress output: ;
% separate statments: ,
% For a full list, see
help punct
% examples)
1+1 % Hi! % evaluate 1+1 and ignore the comment
a = 1; % assign 1 to $a$ and suppress output
a % check the value of $a$ (MATLAB will say 1)
a=1, b=2 % you may use a comma to separate statements
% on the same input line
%==========%
% Keywords %
%==========%
% also called reserved words
% part of the language
% cannot change meaning using assignments
% if, end, while, for (and more to come!)
% Keywords are involved with programming in a big way....
%=========%
% Strings %
%=========%
% Strings are collections of individual characters (usually ASCII)
% They are not names and not keywords.
% Strings are used for processing text files and providing labels.
% To create a string surround characters with single forward quotes:
'hello, I am a string!' % enter a string
% You may also assign a string to a variable:
x = 'blah, blah, blah' % assign a string to $x$
% Characters inside strings have numerical ASCII codes.
% To find out a string's numerical codes, use $double(string)$:
x = 'abc'; % assign a string to $x$
double(x) % determine the string's numerical character codes
% Much more to say on this subject also....
%===========%
% Functions %
%===========%
% A function is an expression with the syntax $name(args)$,
% where $args$ is a sequence of variables separated by commas.
% Entering a function tells MATLAB to run another program that performs
% the tasks the function represents.
% example)
sqrt(4) % take the square root of 4
% MATLAB reports that the answer is 2
% You may include a function in an expression.
% MATLAB performs the desired tasks in the function. If the function
% produces a value (known as returning a value), MATLAB substitutes the
% returned value for the function.
% example)
1 + sqrt(4) % add 1 to square root of 4
% MATLAB will replace sqrt(4) with 2 and then add 2 to 1
% Some functions in MATLAB take may no arguments:
help
% Much more to say on functions....
%-------------------------------------------------------------------------------