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- Lecture 1: Introduction
Lecture
Lecture series based on the text:
Essential MATLAB
for Engineers and Scientists
for
By
By
Hahn & Valentine
Hahn
http://www.mediafire.com/?y5dz4zjxrj0z4
Email: bttu@fetel.hcmus.edu.vn
© 2007 Daniel Valentine. All rights reserved. Published by
Elsevier.
- MATLAB desktop
MATLAB
Command Window
Command History
Command
Window
Window
Workspace Window
Current Directory
Current
Window
Window
Start Button
- Command Window
Command
The Command Window on the right is the main
The Command
panel where you interact with MATLAB.
You key (or type) and commands after
You
the prompt >>; MATLAB executes the commands
>> MATLAB
and displays results (if requested).
and
Some commonly used tools and commands:
(up arrow) returns last command input, can be
returns
repeated
repeated
– clc – clears the screen
– whos – shows list of variables
– clear – clears variables
- Evaluation of MATLAB
Evaluation
HANDSON with MATLAB
– Type
>> 2+3
2+3
into the Command Window
>> clc
>> whos
whos
Throughout the lecture, yellow text indicates
what you should type into MATLAB.
- Command History Window
Command
The Command History Window logs all of the
The Command
commands you enter in MATLAB.
commands
It should have logged 2+3.
It 2+3
Use the Command History Window to reenter 2+3
Use 2+3
in the command window (use copy-and- paste or
double click on 2+3).
double
This is useful to retrieve past commands.
Use “Shift” key to select multiple lines.
Use “Shift”
- Arithmetic with MATLAB
Arithmetic with MATLAB
Let us explore by doing exercises:
>> 3–2
>> 3–2
>> 3*2
>> 3*2
>> 3/2
>> 3/2
>> 3\2
>> 3\2
>> 3^2
>> 3^2
>> 2/0
>> 2/0
>> 0/2
>> 0/2
>> 3*Inf
>> 3*Inf
- Algebraicnumeric computations
Algebraicnumeric computations
Let us explore by doing exercises:
>> a= 3
>>
>> b= 2
>>
>> a– b
>>
>> a/ b
>>
>> a^2
>> a^2
>> c= a*b
>>
>> d= c^(b+1)
>> c^(b+1)
>> who
- Hiding Output
Hiding Output
Let us explore by doing exercises:
>> clear; clc
>> clear;
>> whos
>> whos
>> a = 3;
3;
>> b = 2;
>> 2;
>> c = a * b;
>> b;
>> d = c^(b+1);
c^(b+1);
>> who
>>
>> % a, b, c, d are in workspace
a,
>> a, b, c, d
- Plot y versus x
Plot
Introduction to plotting & displaying data:
>> clear; clc
>> clear;
>> x = 0:0.1:1;
>> 0:0.1:1;
>> y = x.^2;
>> x.^2;
>> whos
>> whos
>> plot(x,y,x,y,’o’)
>> plot(x,y,x,y,’o’)
>> disp(' '),disp('...... x ........ y .....'),disp([x‘ y'])
>>
>> x
>>
>> y
>> % x and y are 1-by-11 arrays of numbers!
>> and
- Write a Simple Program
Write
Consider computing the volume of a cone:
Volume = (pi.*r.^2.*h)./3
radius = 6 inches
height = 12 inches
In the command window key in:
>> clear; clc
>> clear;
>> r = 6
>> h = 12
>> v = (pi.*r.^2.*h)./3
>> whos
- Editor & M-Files
Editor
An M-file in MATLAB is analogous to a txt-
An M-file
file in Microsoft Notepad.
file
An M-file is created in MATLAB text editor.
An text
M-files:
– You can save your programs (i.e., list of
You
executable commands) as M-files.
executable
– You can reopen and modify your program.
– They are useful for “debugging” (correcting
They
errors) as you develop your programs (your
technical computing tools).
technical
- Comments in programs
Comments
Every time you write a program to be saved, it is
Every
helpful for you to comment (i.e., describe) it well.
comment (i.e., it
To insert a comment on a line in the editor or in
To
the Command Window, use the comment
operator %, then type your comment.
MATLAB:
– will not run lines that begin with the comment operator
will
(in the editor comments appear in green).
Comments
– Comments allow you (and others) to more easily
Comments
understand your program.
understand
– When your lines of code are easy to understand, your
When
code will be easier to use later.
code
- Art of well-written code
Art
A well-written program is like literature; it
well-written
contains comments explaining:
contains
– what your program requires as input.
– what the variables in the program represent.
– what your program computes and displays.
It is useful for you to add a set of header
It
comments that include the name of the
program, your name (as the programmer),
and the date the program was created or
modified.
modified.
- Saving code in an M-File
Saving
Open the editor by:
– Entering the command edit in the command window.
Entering edit
– Or click the white-sheet-of-paper icon in the upper left
Or
hand corner directly below file.
hand
Now enter the lines of code to find the volume of a cone:
rr = 4
h = 12
v = (pi.*r.^2.*h)./3
REMARK: If you save it, add header comments and comments
REMARK:
explaining what the program does.
explaining
After you have typed in the code, save it as cone.m.
- This is cone.m in the editor
This
%
% Tool to compute the volume of a cone.
% A simple sample for a first lecture.
% B.H.& Daniel........... January 2007
%
rr = 4; % radius of the cone
h = 12; % height of the cone
v = (pi.*r.^2.*h)./3 % Volume of the cone
- Execute an M-file as a Command
Execute
Now execute (or run) the program by pushing F5,
Now
or by typing on the command line
or
>> cone
cone
– or by clicking the run button. (Note that the run button looks
run
like a page with a down arrow to its left. It can be found below help on
the toolbar of the edit window.)
the
If you entered the code as written on the previous
If
slide you will get an error!
What went wrong?
Repair your program (Change rr = 4 to r = 4.), save it, and
Repair save
(Change
run it again.
run
Now change the height to 24, save and run your
Now
program again.
- Summary
Summary
MATLAB can be used like a hand calculator to do
MATLAB
arithmetic.
You can define (or assign) variables with
You
numbers and expressions to do calculations as
illustrated by the volume-of-cone example.
illustrated
The advantage of saving programs as M-files is
The M-files
that you open it, make changes and/or execute it
again without having to type it all over again.
again
This concludes our overview of MATLAB and a
This
taste of things to come!
taste
nguon tai.lieu . vn
