1.
Objectives
To become acquainted with the computer
lab and MATLAB by playing with and mimicking various commands & copying
output into a Word document. First skim, and then carefully read the entire assignment before starting any tasks.
2.
Starting
MATLAB
Listen
carefully to the instructions given at the beginning of the lab session to find
out where MATLAB is on the public computers in B7 and how to start it. Remember everything, since you will need to
know it all when you start the homework on your own.
Running
MATLAB creates one or more windows on your monitor. Of these, the Command window is the primary place where you interact with MATLAB.
The character string EDU» is the MATLAB prompt in the Student Edition.
Do not type it in the examples
below.
3.
MATLAB,
the calculator
MATLAB can
do simple and advanced math just like a scientific calculator. Try typing
various mathematical expressions in the command window to see what
happens. The symbols for multiplication,
division, addition, and subtraction are *, /, +, and –. MATLAB can handle square roots, powers,
logarithms, and trigonometric operations using its own built-in functions. The
commands for sine, cosine, natural logarithm, and tangent are sin, cos, log, and tan respectively. To find the sine of 6.2 (in radians), for
instance, we would type
EDU» sin(6.2)
Task 1:
Use MATLAB to compute the expression π*sin(13log(12))+10cos(10)
Solution
>> pi*sin(13*log(12))+10*cos(10)
The answer is -5.9537
Record the
answer in a word document called LabOne.doc. Do this by highlighting
the relevant lines in the MATLAB command window with the mouse. Then click on
'Edit' on the menu bar and choose 'Copy.' Now return to the word document and click
on 'Edit' and choose 'Paste'. This will paste the highlighted text from the
Command window into your word document.
Label the pasted text in boldface as Task 1.
4.
Systems
of equations
As is only proper for an
application called MATrix
LABoratory,
we can use MATLAB to solve linear algebra problems. To solve the system of equations
x + 2y + 3z =
366
4x
+ 5y + 6z = 804
7x
+ 8y + 0z = 351
we would type the following commands:
EDU» A = [1 2 3; 4 5 6; 7 8 0];
EDU» b = [366; 804; 351];
EDU» x = A\b
You should discover after typing the last line that the solution is x = 25, y = 22, z = 99.
Task 2:
Study the example to solve the system of
equations
2x + y + z = 10
x
+3 y - z = -21
5x
- y +2 z = 19
Copy the resulting answer in your word
document and label it Task 2.
Solution
EDU>> A = [2 1 1;1 3 -1;5 -1
2]
EDU>> b=[10;-21;19]
EDU>> x = A\b
The answer is:
x =
-2.8462
-0.6154
16.3077
5.
Getting
help in MATLAB
You should become familiar with
the help
and lookfor commands; they will come in
handy later. If you type help followed by a function name
in the Command Window, MATLAB will display help for that function. For
instance, type
EDU» help sin
You can even type help
help. Unfortunately, to use help correctly you must know the
precise name of the function. The lookfor command differs from the help command by searching for
summary information instead of an exact match.
Task 3:
Compare the results of typing help
tangent and lookfor tangent in the Command window. Record the answers for each command in
your word document and label it Task 3.
6.
Letters
in Your Name
We saw today how to create a variable that is a
character array. This type of variable
is also known as a string.
Task 4:
Create a string
variable called myName and store your
name in it. Then use the Matlab help and lookfor functions to find a function in Matlab that will return the number of
letters in myName. Use this function to get the
number of letters in myName. Copy all the relevant lines in
the command window and paste them into your word document. Label it Task
4.
Solution
EDU>> myName = ‘Jane
Doe’
EDU>> help length
EDU>> length(myName)
7.
Just
for fun
A friend once showed me that
typing why
at the command prompt actually works.
Try it & see what happens.
8.
Submitting
Your Work
Type your
name (and your partner’s name if you have one), student ID, and the date at the
top of LabOne.doc. Print the document and sign it along with
your partner. Give the signed assignment
to the teaching assistant.
If you haven’t set up your Net-Print account, go to http://www.cit.cornell.edu/net-print/getstarted.html
to set up your account. You will need a
Net-Print account to print from the Cornell computer labs.