326.212 Homework 4

Due Nov 30, 2021 @ 11:59pm

Chapter 19

Textbook 19.3.1

Problem 1

Textbook 19.4.4

Problem 1, 6

Textbook 19.5.5

Problem 4

Chapter 20

Textbook 20.3.5

Problem 2

Textbook 20.5.4

Problem 1 (scan your drawing and link it with your .Rmd file)

Textbook 20.7.4

Problem 2, 3

Chapter 21

Textbook 21.2.1

Problem 2

Textbook 21.3.5

Problem 3

Textbook 21.4.1

Problem 1

Textbook 21.5.3

Problem 1

Textbook 21.9.3

Problem 3

Chapter 23

Textbook 23.4.5

Problem 3

Chapter 24

Textbook 24.2.3

Problem 2

Textbook 24.3.5

Problem 2

Extra question(s)

1. (Data manipulation)

   1. For the R built-in iris dataset, the following R code is given:

    data(iris)
    swidth.versicolor <- NULL
    for (i in seq_len(nrow(iris)) ) {
            if (iris$Species[i]=="versicolor") {
                    swidth.versicolor <- c(swidth.versicolor, iris$Sepal.Width[i])
            }
    }

   Vectorize the above code.

   2. Type and run the following R code.

    data(iris)
    head(iris$Sepal.Length[iris$Species])

   Explain why you get those results.

2. (Closure) Simply speaking, a closure is a function created by another function.

   1. Guess the output of the following code and explain why you get those results.

    power <- function(exponent) {
      function(x) {
        x ^ exponent
      }
    }
   
    square <- power(2)
    square(2)
    square(4)
   
    cube <- power(3)
    cube(2)
    cube(4)

   2. What do you think the call k() will return? Explain.

    j <- function(x) {
      y <- 2
      function() {
        c(x, y)
      }
    }
    k <- j(1)