Problem 4 – Coding Problems [40 Points]
Function name: timeCount
Inputs: (2)
1. amount of hours (double)
2. amount of minutes (double)
Outputs: (2)
1. total number of seconds (double)
2. percentage of one day (double)
Write a function named timeCount which takes in a number of hours and a
number
of minutes and gives back the total number of seconds and what percentage of
the day it is.
Test Case:
[sec percent] = timeCount(12,30)
sec--> 45000
percent--> 52.0833
Solution:
function [seconds, percent] = time(hours, minutes)
minute_seconds = minutes .* 60;
hour_seconds = hours .* 60 .* 60;
seconds = hour_seconds + minute_seconds;
day = 24 .* 60 .* 60;
percent = (seconds ./ day) .* 100;
end
Problem:
Function Name: SortRotate
Inputs (1):
(double)- a row vector of numbers
Outputs (1):
(double)- the input vector with any number greater than 20 removed, then
sorted, then the vector mirrors itself.
Function Description: Given a vector of numbers, write a function
"SortRotate" which will eliminate any number in the vector greater than 20.
The function will then sort the remaining numbers, and create a mirror image
of itself.
Test Case:
out= SortRotate([1 50 22 3 -5 0 40 2])
out -> [-5 0 1 2 3 3 2 1 0 -5]
Solution:
function out = SortRotate(vector)
a= vector<20;
b=vector(a);
sort_b= sort(b);
c= sort_b(end:-1:1);
out= [sort_b c];
end
Problem:
Inputs (2):
(double)- first row vector
(double)- second row vector
Outputs (1):
(double)- an intertwined row vector
Function description:
Write a function VecMix, which will intertwine two input vectors.
That is, the first element in the first vector input vector is the first
element in the new vector.
The first element in the second input vector is the second element in the new
vector.
The second element in the first vector is the third element in the new vector
and so on.
If one vector is longer than the other, put 0's as place holders.
Test Case:
out = VecMix([2 5 4], [7 6 0 1 3])
out -> [2 7 5 6 4 0 0 1 0 3]
Solution:
function out = VecMix(arr1, arr2)
total= [arr1 arr2];
length_total= length(total);
out= zeros(1,length_total);
c=length(arr1).*2;
d=length(arr2).*2;
out(1:2:c)=arr1(1:1:end);
out(2:2:d)=arr2(1:1:end);
end
Problem:
Function Name: oddsAndEvens
Input (1) : a row vector
Output (1): a row vector contain the following values:
1. the total number of odd numbers
2. the total number of even numbers
3. the total number in the row vector
Function Description: Write a function that will take in a vector as its input and then it will return
a vector whose 1st element will the total number of odd values (NOT POSITIONS) , the 2nd
element will be the total number of even values (AGAIN NOT POSITIONS), and for the 3rd and
final element , the total number of elements in that vector. The output vector again should have a
total of 3 elements.
Hint: try adding true + true in MATLAB.
Test Case:
out = oddsAndEvens([4 9 10 32 14 7])
out --> [2, 4, 6]
Solution:
function newVec = oddsAndEvens(vec)
odds = sum(mod(vec,2)==1);
evens = sum(mod(vec,2)==0);
total = length(vec);
newVec = [ odds evens total];
end
Problem:
Function Name: range5and10
Input (1): a row vector
Outputs(2):
- a modified version of the input row vector with numbers between 5 and 10 removed (inclusive)
- a modified version of the input row vector with numbers not between 5 and 10
removed(exclusive)
Function Description: Write a function that will take in a vector and will first output a row vector
with numbers between 5 and 10 inclusive removed from the original vector. (Inclusive means
you include the numbers 5 and 10). The second output should be a vector that remove all the
numbers inside the original vector that are not in the interval 5 to 10 (exclusive). (Exclusive
means you do not include the numbers 5 and 10).
Test Case:
[out1 out2] = range5and10([6 10 3 14 9 5 7 0])
out1 --> [3 14 0]
out2 --> [6 10 9 5 7]
Solution:
function [out1 out2] = range5and10(vec)
out1 = vec(vec >= 5 & vec <= 10);
out2 = vec(vec < 5 | vec > 10);
end
Problem:
Function Name: sumArr()
Input (1): an array
Output (1): the same array concatenated with sums for its columns and rows and the total sum
like so:
arr is the input
arr =
1
7
0
output
1
7
0
8
2
2
8
=
2
2
8
12
8
6
1
8
6
1
15
11
15
9
35
Function Description: Write function that will take in an array. The output array should be such
that the bottom row of is the sum of all the columns in the inputted array and the leftmost column
is the sum of all the rows. The leftmost number on the bottom row should be the sum of all the
elements in the array.
Solution:
function newArr = sumArr(arr)
newArr = [arr; sum(arr)];
newArr = [newArr sum(newArr,2)];
end
Problem:
Function Description: Write function that takes in an array and sorts the values in successive
columns. When the modified array is given as an output, it has to have the same dimensions are
the original array inputted.
Hint: the reshape() function may be useful
Function Name: sortArr()
Input (1): an array
Output (1): sort an array column-wise in this manner:
arr is the input
arr =
1
7
0
2
2
8
8
6
1
0
1
1
2
2
6
7
8
8
out =
Solution:
function newArr= sortArr(arr)
[ r c] = size(arr);
temp = sort(arr(:));
newArr = reshape(temp,r,c);
end
Problem:
Function Name: ArrayMod()
Input (1):
(double)- an array
Output (1):
(double)- the modified array
Function Description:
Write a function ArrayMod which takes in an array and performs the
following opperations on it:
1 - remove all the even columns.
2 - switch the first and last rows.
3 - divide each odd number by 4.
Test Case;
out = ArrayMod([3 4 1; -1 9 2; 6 7 8])
out -> [6 8; -0.25 2; 0.75 0.25]
Solution:
function modified = ArrayMod(arr)
modified= arr;
modified(:, 2:2:end) = [];
first_row= modified(1,:);
last_row= modified(end, :);
modified(1,:)= last_row;
modified(end,:)= first_row;
modified(mod(modified,2)==1) = modified(mod(modified,2)==1) ./4;
end
Problem:
Function Name: LetterCmp()
Inputs (2):
(char)- a string
(char)- another string
Output (1):
(char)- the letters which appear in the same spot for both strings
Function Description:
Write a function LetterCmp which takes in two strings. The function
returns the letters which are in the same spot (index) for both
strings. It is case sensative. You may assume the longer of the two
words will always be the first input.
Test Case:
out= LetterCmp('Georgia Tech', 'Storage')
out = 'or'
Solution:
function out = LetterCmp(str1, str2)
str1= str1(str1>='a' & str1 <= 'z' | str1>='A' & str1<='Z');
str2= str2(str2>='a' & str2 <= 'z' | str2>='A' & str2<='Z');
positions= find(str1(1:length(str2))==str2);
out= str1(positions);
end
Problem:
Function Name: Compare()
Inputs (2):
(char)- a string
(doulbe)- a vector
Output (1):
(char)- the relationship between the string and vector
Function Description:
You are given a string and a vector. If the length of the string is
greater than the number, return 'String'. If the number is greater
return 'Vector'. If they are both empty, return 'Empty'. If they are
the same length, return 'Equal'
Test Case:
out= Compare('',[])
out -> 'Empty'
out= Compare('CS1371', [2 3])
out ->'String'
Solution:
Problem:
Function Name: study
Input (1): Number of hours the person studied
Output (1): A string commenting on their studying
Description: The function study will take in a number of hours the person studies on a daily basis
and study comments according to these conditions:
If they study less than 4 hours each day say:
'I wish I had your schedule!';
If they study more than 4 but less than 10 hours say:
'Keep up the good work!';
If they study more than 10 hours say:
'You dont sleep do you?'
and if the user does not enter in a valid input, say:
'Please enter hours of study'
Test Cases:
a = study(2)
a --> 'I wish I had your schedule!'
b = study(3)
b --> 'Keep up the good work!'
c = study(18)
c --> You dont sleep do you?
Solution:
Problem:
Write a function called switchAndIf. The inputs and
outputs for the function are defined below:
Inputs(1): a string that usually takes on the values discrete or range
Outputs(1): a string indicating either the input was invalid or a string indicating when to use
switch and if.
Description: The function switchAndIf will indicate when to use switch and ifs based on the
following conditions:
If the following strings are inputted:
'discrete','menu','limited choices' then say:
'Using switch might be a good idea'
if the following strings are inputted:
'range, does not check equality' then say:
'Using if might be a good idea'
You must also return the string: "Invalid input" if the user does not enter a string as their input.
You should return 'Invalid string' if the user inputs a string and it does not match up with the
words stated (e.g. discrete, range, etc.)
Solution:
Problem:
Function Name: slowSort
Inputs (1): - (double) unsorted vector
Outputs (1): - (double) sorted vector
Function Description:
Given an unsorted vector, sort it without calling the function sort. Use
iteration.
Test Case:
out = slowSort([4 -1 0 5 2 5])
out -> [-1 0 2 4 5 5]
Solution:
Problem:
Function Name: modCA
Inputs (1): - (cell) a cell array
Outputs (1): - (cell) the modified cell array
Function Description:
Given a cell array, delete the first and last cells. Then add 1 to
anything that is of type double in the cell.
Test Case:
out = modCA({5, false, 'str', [4 3 2], {3}, 'hi'});
out -> {false, 'str', [5 4 3], {3}};
Solution:
Problem:
Name: locationsVec()
Inputs: a vector
Outputs: an array size 2 x number of elements in the vector
Description: Use a loop( you must use it) through a vector and obtain the value and the position
of that vector. Then outputs an array in such a way that the first row of that array is are the
elements inside that vector and the second row contains the position of that element.
Test Case:
out1 = locationsVec([3, 1, 5])
out1 -> [ 3, 1, 5; 1, 2, 3]
out2 = locationsVec([ 90, 101, -1, 7])
out2 -> [ 90, 101, -1, 7,; 1, 2, 3, 4,]
Solution:
Problem:
Name:createArr()
Inputs: a vector, number of rows(double), number of columns(double)
Outputs: an array
Description: Assuming the user inputs a valid number of rows and columns and also a vector,
reshape the vector into the array of the specified dimensions of rows and columns.
Test Cases:
arr1 = createArr([ 1, 2, 3, 4, 5, 6],2,3)
arr1 -> [ 1 2 3; 4 5 6]
arr2 = createArr([9 1],2,1)
arr2 -> [ 9;1]
arr3 = createArr([ 91, 22, 80, 70, 41, -1, .5, pi], 4,2)
arr3 -> [91, 22; 80, 70; 41,-1; .5, pi]
Solution:
Problem:
Function Name: avgMinMax()
Inputs(1): a string indicating the file's name
Outputs(0): no outputs
Function Description: Create a function that will take in a excel file contain student's test grades.
You can assume the following about the excel file:
1. the first row is will always contain the student's names
2. the first column will also always contain what test the student took
3. second row and on , also the second column and on, you will find only numbers which
represents the student's test scores.
The function should add a header called 'Max Average' on the first column, two rows
after the last test. The maximum average of the students should be stored in the column to
the right. Below 'Max Average' should be 'Min Average' and to the right of that, should
be the minimum student average.
Finally, the function should write the file out to as an excel file with the same name as the
original file name except the word 'Edited_' is now attached to the front of it.
Test Case:
avgMinMax('Student.xls')
Student.xls looks like the following:
'Test/Name'
'Test 1'
'Test 2'
'Test 3'
'Test 4'
[
[
[
[
'Student 1'
61]
63]
100]
92]
'Student
[
[
[
[
2'
92]
79]
87]
92]
'Student 3'
[
82]
[
89]
[
84]
[
92]
Edited_Student.xls should look like the following:
'Test/Name'
'Test 1'
'Test 2'
'Test 3'
'Test 4'
[
[
[
[
'Max Average'
'Min Average'
'Student 1'
61]
63]
100]
92]
'Student
[
[
[
[
2'
92]
79]
87]
92]
'Student 3'
[
82]
[
89]
[
84]
[
92]
[87.5000]
[79]
Solution:
Problem:
Name: dropTest
Inputs(1): A string indicating the file name
Outputs(1): A cell array containing the strings of test names
Description: Create a function that takes in file name. You can assume the following about the
file:
1. the file's 1st row will always contain the students' names as strings.
2. the file's 1st column will always contain the names of the tests each student had to take
3. the 2nd column and on , also the 2nd row and on you can assume this area to be
populated with students' scores (doubles).
Your job is to determine the lowest test score for each student and then output a cell array
containing the names of each of the students in the first row (should be in the same order
as original data), and the test each student should drop in the second row.
Scores.xls looks like the following:
'Test/Name'
'Student 1'
'Student 2'
'Student 3'
'Test 1'
[
61]
[
92]
[
92]
'Test 2'
[
63]
[
79]
[
89]
'Test 3'
[
100]
[
87]
[
84]
'Test 4'
[
92]
[
92]
[
82]
out = dropTest('Scores.xls')
out --> {'Student1', 'Student2', 'Student3';
'Test 1', 'Test 2' , 'Test 4'}
Solution:
Problem:
Function Name: dlmStats
Inputs (3): (char)- a filname
(char) - the delimiter (for reading in the file)
(char) - the delimiter (for writing the file)
Outputs (0)
Function description:
Write a function dlmStats which takes in an dlm file and outputs a modified
dlm file. The delimiter will be specified in the second input.
The inputted file will always have 4 columns.
The first column will always be consecutive integers (i.e. 1, 2, 3, etc) that
correspond to a given team.
The second column will be the number of wins of that team in a given season
The third column will be the total losses that season.
The fourth column will the the number of ties.
The function should create a new array that gives the following statistics
all in the first row:
1 - the ID number of the team with the most wins
2 - the ID number of the team with the most losses
3 - the ID number of the team with the least ties
Write this new array to delimited file which should have the same base name
as the inputted name with '_new' added to the end. The new delimiter is
specified in the third input
Test case:
dlmStats('scores.dlm', '!', '*')
scores.dlm looks like the following:
1!13!0!1!
2!8!4!2!
3!2!7!5!
4!10!4!0!
5!0!13!1!
scores_new.dlm should look like the following:
1*5*4
Solution:
Problem:
Function Name: xlsBaseball
Inputs (1) (char)- a filname
Outputs (0)
Function description:
Write a function xlsBaseball which takes in an excel file and outputs a
modified excel file.
The input excel file will always have 3 columns.
This first column will always have 'Team' in the first row and the names of
the teams under.
The second column will always have 'Runs Scored' in the first row and the
amount of runs scored by each team had under.
The third column will always have 'Runs Allowed' in the first row and the
amount of runs allowed by each team had under.
The function should create a new array which is identical to the excel data
except with one added row to the very bottom.
In this row, the first column should contain 'Totals'.
The second column should contain the total amount of runs scored.
The third column should contain the total amount of runs allowed.
Write this new array to an excel file which should be named the same as the
input, but with the prefix 'new_'
Test Case:
xlsBaseball('baseball.xls')
baseball.xls looks like the following:
'Team'
'Runs Scored'
'Runs Allowed'
'Us'
1024
4
'Them'
1
999
new_baseball.xls should look like the following:
'Team'
'Runs Scored'
'Runs Allowed'
'Us'
1024
4
'Them'
1
99
'Totals'
1025
103
Solution:
Problem:
Solution:
Problem:
Solution:
Problem:
Solution:
Problem:
Solution:
Problem:
Solution:
Problem:
Solution:
Problem:
Solution:
Problem:
11. Character Strings (20 points)
Write a MATLAB function called makeGTEmail that consumes two parameters:
 A character array representing the name of the person
 A domain representing the department the person is associated with. The rest of the
email will always be gatech.edu.
Any spaces in the name of the person should become a “.” in the email address. The function
should return the character array of the newly formed email address. Assume any characters in
the email address will always be lowercase.
Examples:
makeGTEmail(‘david smith’, ‘cc’); should return:
‘david.smith@cc.gatech.edu’
makeGTEmail(‘george p burdell’, ‘ece’); should return:
‘george.p.burdell@ece.gatech.edu’
makeGTEmail(‘clough’, ‘pres’); should return:
‘clough@pres.gatech.edu’
Problem 11
function ret = makeGTEmail(str1, str2)
str1(find(str1==‘ ’)) = ‘.’;
ret = [str1, ‘@’, str2, ‘.gatech.edu’];
Criteria
5 pts correct function header
4 pts finding the spaces correctly (Can use either find or iteration)
4 pts replacing correctly with a '.'
4 pts correct concatenation
3 pts returns the concatenated string (even if it is incorrect)
11. Character Strings (20 points)
Write a MATLAB function called makeWebAddress that consumes two string parameters and
produces a Web address in the form ‘http://www.DDDD.gatech.edu/PPPP, where DDDD is a
department and PPPP the personal information. The parameters are:
 A string representing the name of the person
 A string representing the department the person is associated with.
Any spaces in the name of the person should become a “.” in the email address. The function
should return the character array of the newly formed web address.
Examples:
makeWebAddress(‘/fac/David Smith’, ‘cc’); should return:
‘http://www.cc.gatech.edu/fac/David.Smith’
makeWebAddress (‘~gt12345z’, ‘prism’); should return:
‘http://www.prism.gatech.edu/~gt12345z’
Problem 11
function ret = makeWebAddress(str1, str2)
str1(find(str1==‘ ’)) = ‘.’;
ret = [‘http://www.’, str2, ‘.gatech.edu/’, str1];
Criteria
5 pts correct function header
4 pts finding the spaces correctly (Can use either find or iteration)
4 pts replacing correctly with a '.'
4 pts correct concatenation
3 pts returns the concatenated string (even if it is incorrect)
Problem 4 – Coding Problems [40 Points]
1. You are given a sound of a piano playing a C-note – 'cNote.wav'. Determine the number of
seconds the sound plays for and store in the variable tnote. Then, plot the amplitude of the
sound versus time.
2. Write a script to solve the following equations:
4x – 13y + 2z = 8
5y = z
x – 5z = 42
3. Write a MATLAB function called makeGTEmail that consumes two parameters:
 A character array representing the name of the person
 A domain representing the department the person is associated with. The rest of the
email will always be gatech.edu.
Any spaces in the name of the person should become a “.” in the email address. The function
should return the character array of the newly formed email address. Assume any characters in
the email address will always be lowercase.
Examples:
makeGTEmail(‘david smith’, ‘cc’); should return:
‘david.smith@cc.gatech.edu’
makeGTEmail(‘george p burdell’, ‘ece’); should return:
‘george.p.burdell@ece.gatech.edu’
makeGTEmail(‘clough’, ‘pres’); should return:
‘clough@pres.gatech.edu’
4. Given vectors x and y of equal length containing x and y data values, please do the following:
- Compute the coefficients for a third order fit of the data and store in C
- Create a new y vector called newy using this fit and the original x values
- Compute the cumulative integral of newy using the trapezoidal rule
- Plot the integral versus the x values
Part 3 – Coding [40 points]
1. You are given a vector, temp, of temperature data that you want to “correct”. Your goal is to
write a function named ‘fiddle’ that makes the temperature appear to be increasing over time.
Your function should count the number of entries, N, below the average temperature. It should
then add to those low temperatures in turn values that increase from 1 to N.
For example:
if temp is [ 67 42 97 84 35 37 67 28]
The function fiddle will add [ 0 1 0 0 2 3 0 4]
returning: [ 67 43 97 84 37 40 67 32]
2. Write a script to solve the following equations:
4x – 13y + 2z = 8
5y = z
x – 5z = 42
3. You are given a set of x and y points, and are interested in the difference between a spline fit
and a curve fit. Write a script that calculates the difference between the values of the spline
fit and a curve fit of order 5 at values spaced 5 times closer than the original x data .
4. Write a function called myIsField. The function will take in a structure array and a string and
will produce a logical result. If the field exists in the structure array then the function returns
true. Otherwise it returns false.
You may NOT use the isfield( ) function.
Example:
A = struct('name', 'Justin', 'favoriteclass', 'cs1371')
ret = myIsField(A, 'name')
ret: true
5. Write a function named insertSilence that consumes two inputs: the file name of a .wav
file and the number of seconds of silence to insert, and returns nothing. This function should read
the sound data, then split it into two halves and insert between the halves a vector of silence that
will last for the number of seconds specified by the second parameter. The function should then
plot the sound (with the silence inserted) in the time domain using a red line. Title your plot
'Inserted Silence' and label the x-axis 'time'.
Test Case:
insertSilence('saxophone.wav',3);
Part 3 – Coding [40 points]
1. 'fiddle'
function temp = fiddle(temp)
avg = mean(temp);
lows = temp < avg;
N = length(find(lows));
temp(lows) = temp(lows) + (1:N);
end
2. solve equations
A = [4 -13 2
0 5 -1
1 0 -5]
B = [8 0 42]'
v = A \ B;
x = v(1)
y = v(2)
z = v(3)
3. spline fit and a curve fit
x = 1:5
y = sin(x)
xi = linspace(x(1), x(end), 5*length(x))
diff = spline(x, y, xi) - ...
polyval(polyfit(x, y, 5), xi)
4. myIsField
function res = myIsField(sa, name)
res = false;
flds = fieldnames(sa);
for ndx = 1:length(flds)
if strcmp(name, flds{ndx})
res = true;
break;
end
end
end
5. insertSilence
function insertSilence(name, t)
[snd fs] = wavread(name);
N = t * fs;
snd = [snd(1:end/2); zeros(N,1); snd((n/2+1):end)];
plot(snd, 'r')
title('Inserted Silence')
xlabel('time')
end