Assignment 2

WISE R CLUB, Xiaojun Sun, 2014.07.11

This is the second assignment for WISE R Club members. You’d better read Chapter 5 to Chapter 8 of R in Action before trying to finish this assignment. The questions are described as following.

CONTENTS

Question 1

Write a factorial function with the name Fac by yourself. The function can realize the flowing features: $Fac(n)=1$ if $n=0$ and $Fac(n)=n(n-1)(n-2)…1$ for any integer $n>0$. Please not use the factorial() function provided in R, try to write your own factorial function. Make the function as simple and short as possible.

Question 2

Based on the dataset grades.txt which I gave you in the last assignment, answer the following questions.

Question 2.1

Draw the box plots of the test scores of the three courses: Math, Chinese and English in one graph just like Figure 6.12 in the book.

Question 2.2

Take sum of the test scores of the three courses(Math, Chinese and English), record it as variable Sum. Grade each student from A+ to D based on the 80th, 60th, 40th and 20th percentile of Sum according to the table below. You may refer to Listing 5.6 in the book.

Question 2.3

Write a function named Grade, whose input is the name of one student and output is the grade of him or her.

Question 2.4

Draw a pie chart of the grades: A+, A, B, C and D from table with label for each part of the pie chart. You may refer to Listing 6.5 in the book.

Question 2.5

Divide the students into five groups by the grades: A+, A, B, C and D. Describe the mean and standard error of test scores for each group.

Question 3

Based on the same dataset grades.txt, answer the following questions.

Question 3.1

Regress Math on Chinese and English. Summarize the result and draw a diagnostic plot like Figure 8.6 in the book. See what conclusion you can draw from this plot.

Question 3.2

Draw a histogram of the studentized residuals and superimposes a normal curve, kernel density curve and rug plot. You may refer to Listing 8.6 in the book, but not use that residplot function unless you know how it works.

Notice

1. You need to send your solution in PDF format to my email (xiaojunsunshine@126.com) before Tuesday, 15th July 24:00.
2. You are required to include both the source codes and results in the your solution.
3. The questions are a bit too many. Just go ahead and give it a try. If you feel it’s hard to finish all the questions, you can just finish some of them and send to me.
4. I will write a solution for this assignment and explain it in detail in the next meeting of R Club.
5. I hope you have fun while learning R.

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