Assignment 7

Due: Friday, April 24th

This assignment contains one programming exercise on creating thumbnail images, and one programming problem on the analysis of data on the women's marathon in the summer olympics. These programming tasks provide practice working with strings, cell arrays, and external files. You can turn in your solutions any time on 4/24/20, and only need to submit an electronic copy of your code files. Your electonic submission is described in the section Uploading your completed work (there is no Google form to submit for this assignment). If you need an extension on this assignment, please contact Ellen or Stella. You'll start this assignment work in lab with a partner, but can continue to work independently to complete the assignment.

Reading

The following material in the Gilat text is useful to review for this assignment: 53-55, 103-110. You should also view the lecture videos on strings and cell arrays and reading and writing text files.

Getting Started: Download assign7_files

Use Cyberduck to download a copy of the assign7_files folder from the download folder in the course directory on the CS file server. The assign7_files folder contains a subfolder of images for the programming exercise, a text file named party.txt that you will work with in lab, and a text file named olympics.txt for the programming problem on this assignment.

Uploading your completed work

When you are done with this assignment, your assign7_files folder should contain a new subfolder named thumbs with a set of thumbnail images created in the exercise, and six code files: reduceSize.m, testReduce.m, medalsYear.m, medalsCountry.m, fastestMarathon.m, and testOlympics.m. Use Cyberduck to connect to the CS file server and navigate to your cs112/drop/assign07 folder. Drag your assign7_files folder to this drop folder. More details about this process can be found on the webpage on Managing Assignment Work.

Exercise: Creating Thumbnails for a Folder of Images

This exercise uses a set of MATLAB functions related to managing files and directories: pwd, filesep, dir, and mkdir. You can also explore these functions in the MATLAB Help system. Before starting, set the Current Directory to the assign7_files folder.

Write a function named reduceSize that has two inputs: (1) a matrix that stores an image and (2) a scale factor. This function should have a single output that is a new image matrix. The output image should be a reduced version of the input image, created by sampling the rows and columns at regular intervals given by the input scale factor. For example, given the following function call: 

smallMatrix = reduceSize(originalImage, 4);

the resulting image should be one fourth the size of the original image, created by sampling every 4th row and column of the original image. The reduceSize function can be very short!

Write a script named testReduce.m that tests your reduceSize function for a set of images stored in the images subfolder that is contained inside the assign7_files folder. This script should use the dir function to create a listing of all of the files stored in the images subfolder that have a filename extension of .jpg. It should then create a new folder named thumbs in the assign7_files folder. Finally, it should loop through all the image files and perform the following three steps for each one:

  1. read the image from the images folder into the MATLAB workspace
  2. reduce the image by a factor of 4
  3. store the reduced image in the thumbs folder (using the imwrite function).

Problem: Women's Marathon in the Summer Olympics

In this problem, you'll define three functions and create a testing script that explore data on the medal winners in the women's marathon in the summer olympics, an event that began in 1984. The olympics.txt text file in the assign7_files folder contains data that includes the year, medal, name, country, and finishing time for the winners, as shown in this excerpt: 

year    medal    firstName    lastName    country      time
1984    gold     Joan         Benoit      USA          2:24:52
1984    silver   Grete        Waitz       Norway       2:26:18
1984    bronze   Rosa         Mota        Portugal     2:26:57
1988    gold     Rosa         Mota        Portugal     2:25:40
1988    silver   Lisa         Martin      Australia    2:25:53
1988    bronze   Katrin       Dorre       EastGermany  2:26:21
...

(1) Create a testing script

To begin, create a script named testOlympics.m and add code to read the data from the olympics.txt text file using the fopen, textscan, and fclose functions. As you complete the three functions below, add code to this script to test these functions.

(2) Print data for a particular year

Define a function named medalsYear that has two inputs: (1) the cell array of data returned by the textscan function that includes information on the year, medal, name, country, and time, for all of the medal winners, and (2) a year. This function should print information about the three medal winners for the input year, using the fprintf function to show this data in a nice format. This information can just be printed in the Command Window. In the following example, the cell array of data is called medals: 

>> medalsYear(medals, 2008)
women's marathon winners in 2008:
gold     Constantina  Tomescu      Romania      2:26:44
silver   Catherine    Ndereba      Kenya        2:27:06
bronze   Zhou         Chunxiu      China        2:27:07

(3) Write information for a particular country to a text file

Define a function named medalsCountry that has three inputs: (1) the cell array of data returned by the textscan function that includes information on the year, medal, name, country, and time, for all of the medal winners, (2) a country name, and (3) a file name. This function should write information to a text file with the input file name, about all of the medal winners from the input country. The fprintf function should be used to write this data in a nice format. For example, the following function call: 

>> medalsCountry(medals, 'Kenya', 'KenyaMedals.txt');
should create a new file named KenyaMedals.txt with content that looks something like this: 
women's marathon winners from Kenya
2000   bronze   Joyce        Chepchumba   2:24:45
2004   silver   Catherine    Ndereba      2:26:32
2008   silver   Catherine    Ndereba      2:27:06
2012   silver   Priscah      Jeptoo       2:23:12
2016   gold     Jamima       Sumgong      2:24:04

(4) Who holds the olympic record for the women's marathon?

Define a function named fastestMarathon with a single input that is the cell array of data returned by the textscan function. This function should print information about the olympic record holder for the women's marathon. You can use either the disp or fprintf functions for this printout. For example: 

>>fastestMarathon(medals)
The olympic record for the women's marathon is 2:23:07, set by Tiki Gelana from Ethiopia in 2012
>>

Note: the str2num or str2double functions in MATLAB can be used to convert the string representation of a number to its numerical representation.