Assignment-1 Solution

Description

1 INTRODUCTION

A database management system (DBMS) is a specialized piece of software for managing data. Before DBMSs were invented, applications manage data using what is known as file processing techniques, where the data is stored on the operating system file system and is processed by application programs written in some programming language. The following illustrates the typical processing steps on a single data file.

initialize some book-keeping information I

open data file F

while (F is not empty)

read next record r from F

if (r satisfies some condition) then

do something with r

update I if necessary

do something with I if necessary

close file F

The objective of this assignment is to let you get a sense of what it takes to manage data without using a DBMS.

2 DATABASE

In this assignment, we have a very simple database that consists of a single comma-separated values (CSV) file that maintains the resale flat prices in Singapore from January 1990 to November 2019¹. The file contains a total of 808,472 records, where each record consists of the following sequence of 10 columns:

1. Resale month (YYYY-MM)

2. Town (e.g., ANG MO KIO, YISHUN)

3. Flat type (e.g., 1 ROOM, 2 ROOM, EXECUTIVE, MULTI GENERATION)

4. Block number

¹THE CSV fiLE IS DERIVED FROM https://data.gov.sg/dataset/7a339d20-3c57-4b11-a695-9348adfd7614.

5. Street name

5. Storey range (e.g., 01 TO 03, 49 TO 51)

5. Floor area in square metres

5. Flat model (e.g., DBSS, MAISONETTE, MODEL A)

5. Lease commencement date (YYYY)

5. Resale price

3 WHAT TO DO

You are to attempt AT LEAST ONE of the following five questions. Each question is worth 1 mark, and your score for the assignment is the maximum score of the attempted questions. You are encouraged to attempt all questions to further hone your problem solving and programming skills!

Each question requires writing a program to perform a data management task. Your program should be written using one of the following programming languages: C, C++, Java, Javascript, or Python. Your program should not use any special libraries (e.g., Apache Commons CSV, NumPy, Pandas) to manipulate CSV files; instead, use the programming language’s standard file processing functionalities. Your program should read the input CSV file from standard input.

Question 1: Find all the records with flat model = ’ADJOINED FLAT’ and flat type = ’3 ROOM’.

Output these CSV records (in any order) to the standard output.

Question 2: Compute the following four statistics for each town: (1) the number of resale flat trans-actions, (2) the maximum price per square metre (psm) for the town, (3) the average psm for the town, and (4) the minimum psm for the town. The psm metric is defined as the ratio of resale price to floor area. All psm values should be rounded up to the nearest integer values. Output each town and its four statistics as a single CSV record to the standard output. The output records are to be sorted in descending order of average psm values.

Question 3: Resale transactions can be classified into either good or bad as follows. A resale transaction X is defined to be bad if there is another resale transaction Y where both X and Y are for the same town and they satisfy one of the following conditions:

1. The resale price of Y is higher than that of X, and the floor area of Y is lower than that of X;

2. The resale price of Y is the same as that of X, and the floor area of Y is lower than that of X; or

3. The resale price of Y is higher than that of X, and the floor area of Y is the same as that of X.

A resale transaction that is not classified as bad is considered to be a good resale transaction. Find all the good resale transactions for the town named ’BISHAN’ and output them as CSV records to the standard output sorted in ascending order of resale month values.

Question 4: Compute the cumulative number of resale transactions for the town named ’LIM CHU KANG’ as follows. For each resale month M where there is some transaction for the town named ’LIM CHU KANG’, count the total number of resale transactions for ’LIM CHU KANG’ up till month M. Output the distinct pairs of resale month and total to the standard output. The output CSV records are to be sorted in ascending order of resale month values.

Question 5: Update all the records located in the town ’YISHUN’ by increasing their floor area by 10%. The updated values should be rounded up to the nearest integer values.

4 HOW TO START

Download the following file: https://www.comp.nus.edu.sg/∼cs2102/cs2102-assign1.zip

The unzipped directory contains the following files:

• A CSV database file resale-flat-prices.csv.

• A directory output-files/ which contains an output CSV file for each of the questions. You may use these files to compare against your program outputs.

5 HOW TO SUBMIT

Submit your source code for each of the attempted questions. Each source file should be named using your student number followed by a hyphen and the question number (e.g., your Java program for Question 2 should be named A1234567Z-2.java if your student number is A1234567Z). Upload your source file(s) into the LumiNUS’s Files Folder named Assignment 1 Submissions. Do not submit any CSV files.

This assignment is due on January 31 (Friday, 6pm).

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