CS 112

Assignment 5

Due: Friday, April 3, at 10:00am

You can turn in your assignment up until 10:00am on 4/3/15. You should hand in both a hardcopy and electronic copy of your solutions (it is ok to hand in your hardcopy during your lab on Friday, but the electronic copy should be submitted by 10:00am). Your hardcopy submission should include printouts of five code files: printStudentInfo.m, mostFacebookFriends.m, getFavoriteSong.m, testStudentInfo.m and visualize.m. To save paper, you can cut and paste all of your code files into one file, but your electronic submission should contain the three separate files. Your electronic submission is described in the section Uploading your saved work.


The following new material in the fourth edition of the text is especially useful to review for this assignment: pages 190-197 and 219-229 (third edition: pages 155-165 and 208-216). You should also review notes and examples from Lectures #8, 9 and 12, and Labs #6 and 7.

Getting Started: Download assign5_problems from cs112d

Use Fetch or WinSCP to connect to the CS server using the cs112d account and download a copy of the assign5_problems folder from the cs112d directory onto your Desktop. This folder contains two data files named students.mat and rising_data.mat and one code file named test_visualize.m for the problems in this assignment.

Uploading your completed work

When you have completed all of the work for this assignment, your assign5_problems folder should include five code files, printStudentInfo.m, mostFacebookFriends.m, getFavoriteSong.m, testStudentInfo.m and visualize.m. Use Fetch or WinSCP to connect to your personal account on the CS file server and navigate to your cs112/drop/assign5 folder. Drag your assign5_problems folder to this drop folder. More details about this process can be found on the webpage on Managing Assignment Work.

Problem 1: Facebook Friends and Favorite Songs

In this problem, you are given data about the favorite songs and number of Facebook friends for a group of students, and will create a MATLAB program to perform the tasks of printing all the information about the group of students, accessing the favorite songs of particular students, and determining who has the most Facebook friends. The assign5_problems folder contains a file named students.mat that you can load into the MATLAB workspace. This file contains a single variable named students that is assigned to a vector of 10 elements. Each element of the vector is a structure with three fields that store the name, favorite song, and number of Facebook friends, for a particular student. The three fields of each structure are called name, song, and FBfriends.

Task 1: Print all the student information

Write a function named printStudentInfo that has a single input that is a vector of structures containing student information, as described above. This function should print out all the information stored in the vector, with each student's information printed in a nice format such as the following:

>> printStudentInfo(students)
andrea's favorite song is "Dark Horse" and she has 42 Facebook friends
carol's favorite song is "Team" and she has 61 Facebook friends
jean's favorite song is "Pompeii" and she has 23 Facebook friends

Task 2: Who has the most Facebook friends?

Write a function named mostFacebookFriends that has a single input that is a vector of structures containing student information. This function should return two values, the name of the student with the most Facebook friends and the number of Facebook friends for this student.

Task 3: What is her favorite song?

Write a function named getFavoriteSong that has a two inputs, a vector of structures containing student information and the name of a student (a string). This function should return a string that is the name of the student's favorite song. If the name is not found in the vector, this function should return an empty string. You can assume that the input name is written with all lowercase letters, similar to the names in the students vector, and that all the names are unique. Use a while statement to find the location in the input vector that contains the input name. This loop should stop when the name is found. The strcmp function can be used to compare two strings.

Task 4: Putting it all together

Write a script named testStudentInfo.m that contains code to test all of your functions. In particular, this script should do the following:

  1. load the students.mat file
  2. call printStudentInfo to print out all the student information
  3. call the mostFacebookFriends function and print the values that are returned in a nice format, for example:
    nora has the most Facebook friends, with 142
  4. call the getFavoriteSong function within a loop that keeps asking the user to enter a name, and prints the name and student's favorite song, until the user enters something like x that is an invalid name that can stop the loop. A while statement should be used to implement this loop. If the user types a real name that is not contained in the vector, a message should be printed that indicates this. The following is a sample printout for this part of the script:
    Enter the names of students whose favorite song you'd like to know
    Enter x when you'd like to stop
    Enter a name: jean
    jean's favorite song is "Pompeii"
    Enter a name: elaine
    elaine's favorite song is "Say Something"
    Enter a name: mary
    mary was not found
    Enter a name: vicki
    vicki's favorite song is "Burn"
    Enter a name: x

Problem 2: Rising Data

This problem was inspired by a visualization of rising global temperatures at the Bloomberg Company website. You will write a function to create your own visualization of rising data of this sort, and apply this function to data on rising monthly temperatures in the Boston area over the years from 1880 to 2014, and rising daily Dow Jones Industrial Averages over 51 weeks of 2014. An advantage of defining a function to create this visualization, rather than a script, is that a function can easily be applied to different data sources that are provided through an input to the function.

In the assign5_problems folder, there is a data file named rising_data.mat that contains two variables, temps_data and djia_data. The variable temps_data is assigned to a 135 x 12 matrix, where each row corresponds to a different year (1880 to 2014) and each column corresponds to a different month (January through December). The values stored in the matrix are the average monthly temperatures in degrees Celcius. The variable djia_data is assigned to a 51 x 5 matrix, where each row corresponds to a different week during the year 2014 and each column corresponds to a different weekday (Monday through Friday). The values in this matrix are the closing Dow Jones Industrial Averages for each day. The assign5_problems file also contains a script named test_visualize that loads the data files and calls the visualize function (that you will write) for each of these two data sources. Your visualize function should have five inputs:

  1. a 2D matrix of data where the rows and columns represent different time frames (e.g. years x months or weeks x days)
  2. a string to display as the label of the x axis of the data plot
  3. a string to display as the label of the y axis of the data plot
  4. a string to display as the title of the plot
  5. a cell array of strings to display below the tick marks on the x axis

The two calls to the visualize function in the test_visualize script provide examples of these inputs. Your function should loop through the rows of data in the input data matrix, displaying one after the other on the same figure. If you place a pause in this loop, similar to the pause in your virus function in Assignment 4, the presentation will appear as an animation, similar to the Broomberg visualization mentioned above. As you are looping through the rows of data, when the average of the newly displayed data breaks a record (i.e. the mean of the data values in the new row is higher than the mean of all previously displayed rows), a horizontal dotted line should be displayed at the new record mean data value. Finally, each row of data should be displayed with a different color. The two figures below show the full sets of data that should be visible when the animation is complete. The dotted horizontal lines show the average temperature or Dow Jones values during record breaking years or weeks, respectively. The colors change from "cool" shades of blue to "hot" shades of red as time progresses.


The following are a few guidelines and tips for implementing the visualize function:

We have been using single characters, like 'r' and 'g', to specify the color of a plot. An arbitrary color can be specified with a vector of three values that are each between 0 and 1 and represent the amount of red, green, and blue that combine to create the desired color. When calling the plot function, this color vector can be specified with the 'Color' property, e.g.

     plot(xcoords, ycoords, 'Color', [0.3 0.8 0.7]);

which creates a plot with a teel blue color. MATLAB provides a set of built-in color palettes, or colormaps, that you can view in the MATLAB documentation on the colormap function. Each color palette has a name and is associated with a built-in function of the same name that can be used to generate an n x 3 matrix with red, green, and blue values for a set of n colors that span the palette. One of the palettes, for example, is named jet and spans the colors of the rainbow from blue to red. The function call jet(10) creates a 10 x 3 matrix storing 10 sample colors from blue to red:

>> colors = jet(10)
colors =

         0         0    0.6667
         0         0    1.0000
         0    0.3333    1.0000
         0    0.6667    1.0000
         0    1.0000    1.0000
    0.3333    1.0000    0.6667
    0.6667    1.0000    0.3333
    1.0000    1.0000         0
    1.0000    0.6667         0
    1.0000    0.3333         0

These colors were used in a loop to create the following plot of 10 horizontal lines of different colors:

You are welcome to use any of the built-in colormaps in your implementation. The above specifications for the visualize function do not create an animation that has all the aspects of the visualization of rising global temperatures at the Bloomberg website, but they capture everything that is essential to do for this problem. For up to 5 bonus points, you are welcome to add embellishments, such as additional text on the graphs as the animation progresses, or a different method for coloring the individual plots, similar to the Bloomberg example.