7  Lecture: R Basics

7.1 R Basics lecture

Here’s a recording of this lecture (48 minutes 14 seconds):

Recording

7.2 R Basics slides

PDF slide set

7.3 Questions

7.3.1 Question 1

What does a <- 9; a < - 9 do?

TRUE 9 FALSE -9

7.3.2 Question 2

Given a vector x of length 10, which of the following R code snippets would remove the third element from the vector and assign the result to a new vector y? More than one option may be correct.

y <- x[-3] y <- x[3] <- NULL y <- x[c(1:2, 4:10)] y <- x[1:2, 4:10]

7.3.3 Question 3

Given the following vector:

x <- c(a = 1, b = 2, c = 3)

Which of the following R code snippets will extract only the element corresponding to the name “b”?

x[2] x[“b”] x[x == “b”] x[x > 1]

7.3.4 Question 4

Given the following R code:

x <- 1:6
dim(x) <- c(2, 3)

Which of the following options correctly extracts the second column of the matrix x as a column vector?

x[2, ] x[, 2] x[2] x[, 2, drop = FALSE]

7.3.5 Question 5

Which of the following statements are true about data frames in R?

A data frame is a type of list where all elements must be of the same data type. A data frame is a list where elements can be of different data types. A data frame is a matrix where elements must be of the same data type. A data frame is a list where all elements of the list must be of the same length.