September Assigned: 23
Fall 2011
Due: September 30
E7 Laboratory Assignment 5
The purpose of this lab is to introduce you to cell, structure arrays, and logical, relational operators.
Note: You will use MATLABs publish command (accessible in the Editor window via File ->
Publish Filename) to generate a printable document that contains your code and your answers.
1. You must turn in a printed copy to the homework boxes in room 1109 Etcheverry. Further, you will
need to use the command type to display your functions in your main script. You will not get
credit for the functions you have written unless you display them! Be sure to turn your printout
into the box corresponding to the lab section in which you are registered. The due-date is 12:00 pm
(noon) on September 30.
2. Your primary m-le, which is used to generate the HTML document, and all of the function m-les
that you create must also be uploaded to bSpace (under the Assignments tab) by noon on September
30.
Please (i) have your full name, student ID number, and lab section number at the head of the le and
(ii) name this le lastname middlename firstname lab04.m.
Use the clear;format compact command at the beginning of your script to clear the variables from
the base workspace and format appropriately to reduce the length of the output. If your comments
exceed the page border, highlight the comment and go to Text->Wrap Comment.
In several problems, you are asked to execute a number of given lines, and explain (in a comment before
the line) what the command does. Some lines might produce an error (this is deliberate, on our part).
In that case, after you understand what is the issue, comment out that line (using the % symbol) in
your script le and explain why the error occurred.
1. Run the following commands to create the cell arrays A and B and conrm that they are equal:
begin code
A = {Golden,{Bears},[3,1;4,2]};
B = [{Golden},{{Bears}},{[3,1;4,2]}];
isequal(A,B)
end code
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(a) Run the following commands and explain in a short sentence what each of them does.
begin code
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cellplot(A)
size(A)
end code
(b) Run the following commands and explain in a short sentence what each of them does.
begin code
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A{2}(1)
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A{2}{1}
A{2}{1}(1)
end code
(c) Run the following commands and explain in a short sentence what each of them does.
begin code
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size(A{1})
size(A(1))
size(A{2})
size(A{2}{1})
size(A(2))
end code
(d) Create the cell array C as follows:
begin code
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C = {A{1};A{2}{1};A{3}([1 2],[2 1])};
end code
Use celldisp to display the contents of C. What are the major dierences between A and
C?
(e) Perform the following operations on the cell array A with a single line command each:
Put the string Golden in reverse order in cell array A.
Change the second column of the 2D array in cell array A to [10;7].
2. Create the following 2x2 cell array D, dened as follows:
Motor 28C
D=
39
72
Test ID 6
{Tom Alex Sue}
(a) Using celldisp and cellplot, display the content of D.
(b) Using the appropriate cell array addressing, get the number 3 from D and display it (i.e., the
(1,1) element of the content of the (2,1) cell of D).
(c) Using the appropriate cell array addressing, get the string Motor from the string contained
in the (1,1) cell of D and display it.
(d) Extract the number 6 from the (1,2) cell of D and multiply its numerical value with 5.
(e) Notice that the (2,2) element of D contains a cell array. Extract this cell array (i.e. {Tom
Alex Sue}) from D, and assign it to a variable called names. Using sortrows, put the
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elements of names in alphabetical order. Although not stated explicitly in MATLAB help,
sortrows also works on rows of cell arrays. You will need to transpose the cell array names
before using the sortrows function and transpose the result again to end up with a 1x3 cell
array. Then, replace the original cell array in D with new sorted version so that D now looks
like
D=
Motor 28C
39
72
Test ID 6
{ Alex Sue Tom}
Display the resulting cell array D using cellplot.
39
from D and assign it to a variable temp. Explain the dierence
72
between the following commands.
begin code
(f) Extract the matrix
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mat2cell(temp,[2],[2])
mat2cell(temp,[1 1],[1 1])
end code
(g) Using mat2cell, convert temp to a 2x2 cell array. Assign the character string abc to
the diagonal entries of temp (i.e., the elements (1,1) and (2,2)). Then, replace the original
matrix in D with the new cell array temp so that D now looks like
D=
Motor 28C
abc
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abc
Test ID 6
{ Alex Sue Tom}
Display the resulting cell array D using cellplot.
3. In this problem you will create a structure array called class score with the elds: name, grade,
tests and average. The contents of the elds are summarized in the table below. Note that
the contents in 4th row of the structure array are initially empty.
Name
Letter Grade
Test Scores
Average
Anne
A
[90,30,50,100]
Randy
B
[10,20,50,60]
Luke
A+
[100,100,100,90]
The following commands demonstrate the creation of the rst structure of the structure array as
a example. Similarly, create the next 2 structures of class score.
begin code
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class_score(1).name = Anne;
class_score(1).grade = A;
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Assigned: September 23
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class_score(1).test = [90, 30, 50, 100];
class_score(1).average [];
end = code
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(a) Display the eld names of class score using the function fieldnames.
(b) Assign the score that Randy had in his 3rd test (i.e., 50) to a variable Randy test3.
(c) Extract and display Annes test scores that are above 80 with a one-line expression using the
find command.
(d) Extract all the test scores from class score into a comma-separated list, which should
contain all 12 scores. Use the MATLAB command reshape to put the list of 12 scores into
a 3x4 2D array variable called all scores, in which each row contains 4 scores of each
student. Do this part with a one-line command.
(e) Use the MATLAB command mean to compute average scores for each student with the 2D
array all scores, assign the average scores to a 1x3 array named all averages. Also
assign all average scores to their respective average eld in class score.
(f) Using the MATLAB command sort, sort the contents of array all averages in ascending
order and assign the sorted scores to the array sorted averages. Also, assign the sorting
indices to an array named ind.
(g) Using the results of the previous section, sort class score in descending order of average
test score. In other words, the 1st element in the new structure array should belong to the
student with highest average test score. Display the contents in the name eld of the
resulting structure array.
4. (a) Run the following lines of code and explain what each of lines 4-20 does with a short sentence.
begin code
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clear
x = 10;
y = -56;
x>y
x==y
x=y;
x~=y
1&1
a = 1|0
1&2
0&1
isnumeric(a)
isnumeric(p)
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isnumeric(5)
isscalar([1 7])
ts = true
fs = false
class(ts)
class(fs)
class(ts*fs)
end code
(b) Dene again the variables x=10 and y=-56. Execute the following commands and explain
the results.
begin code
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(abs(y)-x)>0 & y<x
(x+y)/2+23==1 | x~=5
(rem(20,4)==0 & rem(20,10))==0
(rem(20,4)==0 | rem(20,10))==0
end code
(c) Let a=1, b=0 and c=1 and run the following commands:
begin code
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a|b
a&b
a|c&b
(a | c) & b
a & (c | b)
~a & c
~(a | b | c)
end code
(d) Explain the output of the following statement in detail:
begin code
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5 > 2+4|~2+5==5
end code
5. (a) Run the following lines of code and explain what they do with short sentences:
begin code
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clear
x = 10;
A = [3 15 1 14 7];
B = [10 2 13 15 19];
x>A
x<B
x>A & x<B
find(x>A)
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find(x>A & x<B)
any(x>A)
any(x==B)
all(x>A)
all(A>B & A>x)
any(A>B & A>x)
end code
(b) Run the following lines of code and explain what each does with a short sentence. If there
is an error running the code, comment the line out and write an explanation for the error.
Note: In the following code, the variable aa is undened intentionally.
begin code
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clear
a = (1>2
a = (1>2
b = (1<2
b = (1<2
&& 1/aa>1)
& 1/aa>1)
|| 1/aa>1)
| 1/aa>1)
end code
6. Logical Indexing: Execute the following lines of code and comment on what each line does.
begin code
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M = [-2 1 3 0 0; 5 4 3 2 1; -4 -5 -6 -7 -8;10 11 12 13 14];
rowIdx = [3 4];
colIdx = [1 3 5];
M(rowIdx,colIdx)
rowIdx = logical([0 0 1 1]);
colIdx = logical([1 0 1 0 1]);
M(rowIdx,colIdx)
rowIdx = [0 0 1 1];
colIdx = [1 0 1 0 1];
M(rowIdx,colIdx)
end code
7. Trey, Mike, and Page are all taking Music History 101 together. Their respective quiz scores are
stored in 1-by-6 arrays as follows:
begin code
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Trey = [78 34 75 87 90 65];
Mike = [54 50 67 85 74 72];
Page = [80 20 50 87 45 60];
end code
Using the relational operators and other related MATLAB functions, write one line of code for
each case below that will return:
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Assigned: September 23
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(a)
TRUE, if for every quiz Trey does not have the lowest score;
FALSE, if there is at least one quiz where Trey has the lowest score.
(b)
TRUE, if for every quiz Trey got the highest score among the three;
FALSE, if there is at least one quiz in which Trey did not score the highest.
(c)
TRUE, if there is any quiz in which Trey scored the highest;
FALSE, if Trey never scored the highest in all the quizzes.
(d) The quizzes that Trey scored the highest out of the class.
8. A piecewise function is dened as follows:
1/(x + 1),
1,
y = x2 ,
1,
1/(x 1),
if
if
if
if
if
x 2
2 x 1
.
1x1
1x2
2x
Write a MATLAB function based on the description above using the if-elseif-else construct.
The header of this function should be:
begin code
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function y=fcn_prb7(x)
end code
Evaluate the function for x= -10, 0, 2 and 1000.
9. Suppose that the income tax for individuals is dened as follows: the rst $50,000 are taxed at
10%, the next $50,000 at 15%, and the subsequent $100,000 at 20%. Finally income exceeding
$200,000 is taxed at 25%. Write a MATLAB function named taxcalc that takes the income,
inc, as the input and outputs the eective tax rate, taxr, that is the actual percentage of tax
assessed based on the preceding rules. Use an if-elseif-else programming construct to write
the function.
Execute the function to determine the eective tax rate for incomes of $10,000, $100,000,
$250,000 and $1,000,000.
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