# 2013F002/HW4

Homework 4

Due Tuesday 1 October 2013. Name:___________________________________ Section: (9am or 10:15am)

# 1. Accessing MATLAB

To answer these questions, you will need access to MATLAB using any one of the options given at Introduction_To_MATLAB. You don't need to know what the commands mean - this is only a check that you are able to get MATLAB to work.

Hint: To prevent transcription errors, copy and paste these commands on to the MATLAB command line. If you are using MATLAB through the VCL and you are using a Mac, you will need to use CTRL C (command C on Mac) to copy from your browser and control v (command V on Mac) to paste onto the MATLAB command line.

• Start MATLAB and enter rand(1) on the command line. Write down what you see after you press enter.

• Enter sprintf('%d ','last name') on the command line except replace last name with your last name. Write down what you see after you press enter. Extra credit: What do the numbers mean?

• Enter version on the command line. Write down what you see after you press enter.

• Enter for on the command line, do not press return but instead press the "F1" button (or fn F1 on a Mac) to the upper left of your keyboard. Describe what you see.

rand(1)
since this generates a random number,
you'll get a different number everytime you run it

sprintf('%d ','Weigel')
87 101 105 103 101 108
these numbers represent the ASCII code for your last name
87=W 101=e 105=i 103=g 101=e 108=l

version
8.1.0.604 (R2013a)

for
Help window pops up which has an explanation of what
for command does and how it's used


# 2. Valid Names

Which of the following are valid names for a variable? State the reason for your answer. (See the module on Assignment#General_Syntax_Rules for syntax rules.)

• c..v
• c_v
• one_my
• 1_my
• A1^3
• A1cubed
• A/B*C

c_v
one_my
A1cubed


# 3. Array Syntax I

See the module on Arrays and Arrays#Questions for help with answering this question. You should be able to answer this question without using MATLAB (on the Mid-term there will be similar questions and you will not have access to MATLAB).

Describe what would happen if you entered the following on the command line:

clear;
A(1) = 1;
A = [3,4,5,6];
A(1)


Describe what would happen if you entered the following on the command line:

clear;
Q = [10.1,10.2,10.3];
Q(3)+Q(2)


Describe what would happen if you entered the following on the command line:

Q(1)=Q(3)+Q(2);


What are the values of the elements of Q after you enter the above set of commands?

ans = 3; you'll see the first element of array A


ans = 20.5; you'll see the sum of the third and second elements of array A


the resulting sum, 20.5, will be assigned to the first element of array A
if you type Q(1), you will now see 20.5, instead of 10.1


# 4. Array Syntax II

See the module on Arrays and Arrays#Questions for help with answering this question. You should be able to answer this question without using MATLAB (on the Mid-term there will be similar questions and you will not have access to MATLAB).

A.) Describe the problem with the following sets of commands.

clear;
z = 10;
A(0) = z;


B.) Is there a problem with the following sets of commands?

clear;
z = 10;
n=2;
A(n-1) = z


C.) what is the value of A(n-1) in part B.)?

A(0); the index number, number inside the parenthesis, must be greater than 0


No


10. Since n=2, A(n-1) = A(2-1) = A(1); since z=10, A(1)=10


# 5. Array Syntax III

See the module on Arrays for help with answering this question. You should be able to answer this question without using MATLAB (on the Mid-term there will be similar questions and you will not have access to MATLAB).

Which of the following (circle each one that applies)

• A = [1:7];
• A = [1:2:7];
• A = [1:7:2];
• A = [1,2,3,4,5,6,7];
• A = [1,3,5,7];
• A = [1,3,[5:2:7]];
• A = [1,7,5,3];

is the same as entering

A(1) = 1;
A(4) = 3;
A(3) = 5;
A(2) = 7;


Answer: A = [1,7,5,3]